Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No. )


CORESITE REALTY CORPORATION
(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)
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You are cordially invited to the CoreSite Realty Corporation 2014 Annual Meeting of Stockholders (the "Annual Meeting") to be held on Thursday, May 29, 2014, at 3:00 p.m., Pacific Time. The Annual Meeting will be held at The Fairmont San Jose, 170 South Market Street, San Jose, California 95113.

At the Annual Meeting, you will be asked to (i) elect seven directors to our Board of Directors, (ii) ratify the appointment of KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2014, (iii) approve an advisory resolution on executive compensation and (iv) transact such other business as may properly come before the meeting or any postponements or adjournments thereof.

The accompanying Notice of 2014 Annual Meeting of Stockholders describes these matters. We have elected to provide access to our proxy materials on the Internet under the U.S. Securities and Exchange Commission's "notice and access" rules. Our proxy materials are available at www.proxyvote.com. We have sent the Notice of 2014 Annual Meeting of Stockholders to each of our stockholders, providing instructions on how to access our proxy materials and our 2013 Annual Report on the Internet. Please read the enclosed information carefully before submitting your proxy.

Please join us at the meeting. Whether or not you plan to attend, it is important that you authorize your proxy promptly. If you do attend the meeting, you may withdraw your proxy should you wish to vote in person.

NOTICE IS HEREBY GIVEN that the 2014 Annual Meeting of Stockholders (the "Annual Meeting") of CoreSite Realty Corporation, a Maryland corporation, will be held at The Fairmont San Jose, 170 South Market Street, San Jose, California 95113, on Thursday, May 29, 2014, at 3:00 p.m., Pacific Time, for the following purposes:

We know of no other matters to come before the Annual Meeting. Only stockholders of record at the close of business on April 2, 2014, are entitled to notice of and to vote at the Annual Meeting or at any postponements or adjournments thereof.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE 2014 ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 29, 2014. Our Proxy Statement and 2013 Annual Report are available at www.proxyvote.com.

Regardless of the number of shares of common stock you hold, as a stockholder your role is very important and the Board of Directors strongly encourages you to exercise your right to vote.

2014 PROXY STATEMENT—SUMMARY

This summary highlights information contained elsewhere in this Proxy Statement. This summary does not contain all of the information you should consider. You should read the entire Proxy Statement carefully before voting.

GENERAL INFORMATION
(see pages 1-4)

Meeting:    2014 Annual Meeting of Stockholders
Date:    Thursday, May 29, 2014
Time:    3:00 p.m., Pacific Time
Location:    The Fairmont San Jose, 170 South Market Street, San Jose, California 95113
Record Date:    April 2, 2014
Common Stock Outstanding as of Record Date:    21,629,362 shares

Stock Symbol:    COR
Exchange:    NYSE
Registrar & Transfer Agent:    American Stock Transfer & Trust Company, LLC

State of Incorporation:    Maryland
Year of Incorporation:    2010
Public Company Since:    September 2010

Corporate Headquarters:    1001 17th Street, Suite 500, Denver Colorado 80202
Corporate Website:    www.coresite.com
Investor Relations Website:    www.coresite.com/investors
Annual Report:    www.coresite.com/investors/shareholder-
resources/annual-meetings-material

2013 BUSINESS HIGHLIGHTS
(see page 23)

•: Total shareholder return in 2013 of 20.6%.
•: Revenue in 2013 grew by 13.5% over 2012, with data center revenue in 2013 growing 14.3% over 2012.
•: EBITDA (as defined herein) in 2013 grew by 23.5% versus 2012.
•: Funds from operations (FFO) (as defined herein) attributable to common shares and units in 2013 grew by 18.5% versus 2012.
•: Maintained six nines of up time across our platform for third consecutive year.
•: Continued to expand our properties in New Jersey, Virginia and California.

EXECUTIVE COMPENSATION HIGHLIGHTS
(see pages 22-37)

2013 Say-on-Pay Vote: Approximately 97% of the votes cast at the 2013 Annual Meeting of Stockholders approved the advisory resolution to approve the compensation of our named executive officers. As a result, the Compensation Committee did not materially change its approach to executive compensation in 2013.

2013 Compensation Mix:


CEO:		19% Fixed Salary 81% Performance or Stock Price Variable
Other NEOs:		30% Fixed Salary 70% Performance or Stock Price Variable

2013 Cash vs. Equity Compensation:


CEO:		38% Cash 62% Long-Term Equity
Other NEOs:		48% Cash 52% Long -Term Equity

CORPORATE GOVERNANCE
(see pages 13-19)

Director Nominees: 7
Robert G. Stuckey (Independent)(Chairman)
Thomas M. Ray (Management)
James A. Attwood, Jr. (Independent)
Michael Koehler (Independent)
Paul E. Szurek (Independent)
J. David Thompson (Independent)
David A. Wilson (Independent)

Director Term:    One year
Director Election Standard:    Plurality
Board Meetings in 2013:    9
Executive Sessions:    Yes

Standing Board Committees (Meetings in 2013): Audit (7), Compensation (4), Nominating/Corporate Governance (4)

Independent Board Committees: All

Stock Ownership Guidelines: Yes
Corporate Governance Materials:
www.coresite.com/investors/corporate-governance

ANNUAL MEETING AGENDA
(Board Recommendation)

Election of Seven Directors ("FOR")

Ratification of Appointment of KPMG LLP as Independent Registered Public Accounting Firm ("FOR")

Advisory Resolution to Approve Compensation of Named Executive Officers ("FOR")

Transact Other Business That May Properly Come Before the Meeting

This proxy statement will first be made available to stockholders on or about April 9, 2014. This proxy statement is furnished by the Board of Directors (the "Board") in connection with its solicitation of proxies for CoreSite Realty Corporation's 2014 Annual Meeting of Stockholders (the "Annual Meeting") to be held on Thursday, May 29, 2014, at 3:00 p.m., Pacific Time, at The Fairmont San Jose, 170 South Market Street, San Jose, California 95113, and at any postponements or adjournments thereof. Unless the context requires otherwise, references in this proxy statement to "CoreSite," "we," "our," "us" and "our company" refer to CoreSite Realty Corporation, a Maryland corporation, together with its consolidated subsidiaries, including CoreSite, L.P., a Delaware limited partnership of which CoreSite Realty Corporation is the sole general partner (our "Operating Partnership"), and CoreSite Data Center Services, Inc., a Delaware corporation, our taxable REIT subsidiary.

Pursuant to rules adopted by the U.S. Securities and Exchange Commission ("SEC"), we have elected to provide access to our proxy materials via the Internet. Accordingly, we are sending a Notice of Internet Availability of Proxy Materials (the "Notice") to our stockholders entitled to notice of and to vote at the Annual Meeting. Stockholders will have the ability to access the proxy materials at www.proxyvote.com or request to receive a printed set of the proxy materials by mail or an electronic set of materials by email. Instructions on how to access the proxy materials over the Internet or to request a printed copy may be found in the Notice. In addition, stockholders may request to receive proxy materials in printed form by mail or electronically by email on an ongoing basis. We believe these rules allow us to provide our stockholders with the information they need, while lowering the cost of delivery and reducing the environmental impact of our Annual Meeting.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE 2014 ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 29, 2014. Our Proxy Statement and 2013 Annual Report are available at www.proxyvote.com.

Certain of our directors, officers and employees may solicit proxies by telephone, personal contact, or other means of communication. They will not receive any additional compensation for these activities. We also have retained Eagle Rock Proxy Advisors to assist in the solicitation of proxies for an estimated fee of $5,500, plus reimbursement of reasonable expenses. In addition, brokers, banks and other persons holding common stock on behalf of beneficial owners will be requested to solicit proxies or authorizations from beneficial owners. We will bear all costs incurred in connection with the preparation, assembly and mailing of the proxy materials and the solicitation of proxies and will reimburse brokers, banks and other nominees, fiduciaries and custodians for reasonable expenses incurred by them in forwarding proxy materials to beneficial owners of our common stock.

No person is authorized to give any information or to make any representation not contained in this proxy statement, and, if given or made, you should not rely on that information or representation as having been authorized by us. The delivery of this proxy statement does not imply that the information herein has remained unchanged since the date of this proxy statement.

The purposes of the Annual Meeting are to: (1) elect seven members to the Board to serve until the next meeting of stockholders and until their successors are duly elected and qualify (Proposal One); (2) consider and vote upon the ratification of the appointment of KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2014 (Proposal Two); (3) consider and vote upon the advisory resolution to approve the compensation of our named executive officers (Proposal Three); and (4) transact such other business as may properly come before the Annual Meeting or any postponement or adjournment thereof. Our Board knows of no other matters to be brought before the Annual Meeting.

The close of business on April 2, 2014, has been fixed as the record date (the "Record Date") for the determination of stockholders entitled to receive notice of and to vote at the Annual Meeting. Only stockholders of record as of the close of business on the Record Date are entitled to receive notice of, to attend, and to vote at the Annual Meeting. On the Record Date, our outstanding voting securities consisted of 21,629,362 shares of common stock. Each share of common stock is entitled to one vote. Votes may not be cumulated.

If your shares are registered directly in your name with our transfer agent, American Stock Transfer & Trust Company, LLC, you are considered the stockholder of record with respect to those shares, and the Notice was sent directly to you by us. You may authorize your proxy via the Internet by following the instructions provided in the Notice. If you request printed copies of the proxy materials by mail, you may also authorize your proxy by filling out the proxy card included with the materials or by calling the toll-free number found on the proxy card.

If your shares are held in an account at a brokerage firm, bank, broker-dealer, or other similar organization, then you are the beneficial owner of shares held in "street name," and the Notice was forwarded to you by that organization. The organization holding your account is considered the stockholder of record for purposes of voting at the Annual Meeting. As a beneficial owner, you have the right to instruct that organization on how to vote the shares held in your account. Those instructions are contained in a "vote instruction form." If you request printed copies of the proxy materials by mail, you will receive a vote instruction form. You should instruct your broker or nominee how to vote your shares by following the voting instructions provided by your broker or nominee.

In addition, you may vote in person at the Annual Meeting as described below under the heading "Attending and Voting at the Annual Meeting."

Only stockholders as of the Record Date, or their duly appointed proxies, may attend the Annual Meeting. Stockholders may be asked to present valid picture identification such as a driver's license or passport and proof of stock ownership as of the Record Date. If you are not a stockholder of record but hold shares through a broker or nominee (i.e., in street name), you should provide proof of beneficial ownership on the Record Date, such as your most recent account statement, a copy of the voting instruction card provided by your broker, trustee or nominee, or other similar evidence of

ownership. The use of cell phones, smartphones, pagers, recording and photographic equipment and/or computers is not permitted in the meeting rooms at the Annual Meeting.

Shares held in your name as the stockholder of record may be voted in person at the Annual Meeting. If you are not a stockholder of record but hold shares through a broker or nominee (i.e., in street name), you may vote your shares in person only if you obtain a legal proxy from the broker, trustee or nominee that holds your shares authorizing you to vote the shares. Even if you plan to attend the Annual Meeting, we recommend that you also authorize your proxy or submit voting instructions prior to the meeting as described below so that your vote will be counted if you later decide not to attend the meeting.

Whether you hold shares directly as the stockholder of record or beneficially in street name, you may direct how your shares are voted without attending the Annual Meeting. If you are a stockholder of record, you may authorize your proxy to vote your shares, either by mail or via the Internet, or by calling the toll-free number found on the Notice and the proxy card.

Proxies authorized properly via one of the methods discussed above will be voted in accordance with the instructions contained therein. If the proxy is authorized but voting directions are not made, the proxy will be voted "FOR" each of the seven director nominees, "FOR" the ratification of the appointment of KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2014, "FOR" the advisory resolution to approve the compensation of our named executive officers as described in this proxy statement and in such manner as the proxy holders named on the proxy (the "Proxy Agents"), in their discretion, determine upon such other business as may properly come before the Annual Meeting or any postponement or adjournment thereof.

If your shares of common stock are held through a broker, bank or other nominee (collectively referred to as "brokers"), under applicable rules of the New York Stock Exchange (the "NYSE") (the exchange on which our common stock is traded), the brokers will vote your shares according to the specific instructions they receive from you. If a broker that holds shares of our common stock for a beneficial owner does not receive voting instructions from that owner, the broker may vote on the proposal if it is considered a "routine" matter under the NYSE's rules, including this year's ratification of the appointment of KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2014, or leave that owner's shares unvoted. Pursuant to the rules of the NYSE, the election of directors and the vote on the advisory resolution to approve the compensation of our named executive officers are not "routine" matters as to which brokerage firms may vote in their discretion on behalf of clients who have not furnished voting instructions.

The proposals set forth in this proxy statement constitute the only business that the Board intends to present at the Annual Meeting. The proxy does, however, confer discretionary authority upon the Proxy Agents or their substitutes, to vote on any other business that may properly come before the Annual Meeting. If the Annual Meeting is postponed or adjourned, the Proxy Agents can vote your shares on the new meeting date as well, unless you have revoked your proxy.

Holders of a majority of our outstanding common stock entitled to vote must be present, in person or by proxy, at the Annual Meeting for a quorum to exist. If the shares present in person or by proxy at the Annual Meeting do not constitute a quorum, the Annual Meeting may be adjourned by the chairman of the Annual Meeting to a subsequent time. Shares that are voted "FOR," "AGAINST," "ABSTAIN," or, with respect to the election of directors, "WITHHOLD," will be treated as being present at the Annual Meeting for purposes of establishing a quorum. Accordingly, if you have returned a valid proxy or attend the Annual Meeting in person, your shares will be counted for the

purpose of determining whether there is a quorum, even if you wish to abstain from voting on some or all matters at the Annual Meeting. "Broker non-votes" will also be counted as present for purposes of determining the presence of a quorum. A broker non-vote occurs when a bank, broker or other person holding shares for a beneficial owner does not vote on a particular proposal because that holder does not have discretionary voting power for that particular item and has not received voting instructions from the beneficial owner.

With respect to Proposal One, you may vote "FOR" all nominees, "WITHHOLD" your vote as to all nominees, or "FOR" all nominees except those specific nominees from whom you "WITHHOLD" your vote. A properly executed proxy marked "WITHHOLD" with respect to the election of one or more directors will not be voted with respect to the director or directors indicated. Members of the Board are elected by a plurality of votes cast. This means that the seven nominees who receive the greatest number of "FOR" votes cast will be elected. Cumulative voting is not permitted. Neither broker non-votes nor votes marked "WITHHOLD" will have an effect with respect to the election of any nominee.

You may vote "FOR," "AGAINST" or "ABSTAIN" on Proposals Two and Three. To be approved, each of Proposals Two and Three must receive the affirmative vote of a majority of the votes cast, in person or by proxy, at the Annual Meeting on the proposal. Abstentions and broker non-votes, if any, will not be counted as votes cast on Proposals Two and Three and will have no effect on the result of this vote.

Any proxy as to which no instructions are given will be voted in accordance with the foregoing recommendations.

You may revoke your proxy at any time prior to it being exercised by (i) delivering a written notice of revocation to our Secretary, (ii) filing a duly executed proxy bearing a later date with us or (iii) attending the Annual Meeting and voting in person. Attendance at the Annual Meeting will not, by itself, revoke a duly executed proxy.

The voting results will be tallied by the inspector of election appointed for the meeting and filed with the SEC in a Current Report on Form 8-K within four business days following the Annual Meeting.

Currently, there are seven directors on our Board. The seven persons named below, each of whom currently serves on our Board, have been recommended by our Nominating/Corporate Governance Committee and nominated by our Board to serve on the Board until our 2015 Annual Meeting of Stockholders and until their respective successors are elected and qualify. The Board has no reason to believe that any of the persons named below as a nominee for our Board will be unable, or will decline, to serve as a member of the Board if elected. Each of the nominees has consented to being named in this proxy statement. In addition, the Board has determined that all of our directors, other than Mr. Ray, are independent under applicable SEC and NYSE rules. In making their independence determination, the Board considered the relationship of Messrs. Attwood and Stuckey with The Carlyle Group L.P. ("Carlyle"), the majority holder of our Operating Partnership. A plurality of votes cast is necessary for the election of a director. There is no cumulative voting in the election of directors.

The Nominating/Corporate Governance Committee has not set forth minimum qualifications for Board nominees. However, pursuant to its charter, in identifying candidates to recommend for election to the Board, the Nominating/Corporate Governance Committee considers the following criteria:

The Board does not have a formal policy specifying how diversity of background and personal experience should be applied in identifying or evaluating director candidates. A director candidate's background and personal experience, however, will be significant in the Board's candidate identification and evaluation process to help ensure that the Board remains aware of and responsive to the needs and interests of our customers, stockholders, employees and other stakeholders.

Under the partnership agreement governing our Operating Partnership (the "Operating Partnership Agreement"), Carlyle, which directly or indirectly holds 53.8% ownership of our Operating Partnership, is currently entitled to nominate up to two directors for election to our Board. (See "Information about our Board of Directors and its Committees" for more information about the circumstances under which Carlyle is entitled to appoint nominees to our Board.) Carlyle has exercised this right by nominating James A. Attwood, Jr. and Robert G. Stuckey for election at the Annual Meeting.

The table below sets forth the names and biographical information of each of the directors nominated for election at the Annual Meeting.

Robert G. Stuckey has served as a director since September 2010. Mr. Stuckey is a Managing Director and Fund Head, US Real Estate, at Carlyle. Prior to joining Carlyle in 1998, Mr. Stuckey was Chief Investment Officer at CarrAmerica Realty Corporation ("CarrAmerica"), a real estate investment trust ("REIT"). Prior to that, he was Senior Vice President of Prologis, Inc. ("Prologis"), a REIT which is an owner, operator and developer of industrial real estate, and Chief Financial Officer for Trammel Crow Company, N.E., a developer of, and investor in, commercial real estate. Mr. Stuckey was twice an Academic All-American in football at the University of Nebraska and received an M.B.A. from Harvard University. In determining Mr. Stuckey's qualifications to serve on our Board, the Board considered, among other things, Mr. Stuckey's significant experience concerning the acquisition, disposition, financing, operations and market opportunities of data center properties and private and publicly traded REITs, which provides us with valuable insight into commercial real estate, REIT and data center industry trends that affect our business.

Thomas M. Ray is our President and Chief Executive Officer and a member of our Board since September 2010. Mr. Ray has been responsible for our company's activities since its founding in 2001. From 1998 to September 2010, Mr. Ray served in roles of increasing responsibility, including Managing Director, at Carlyle, focusing upon opportunities for the firm's real estate funds and leading those funds' activities in the data center sector. He brings over 25 years of experience making and managing investments and businesses throughout the U.S., Europe and Asia. Prior to joining Carlyle, Mr. Ray held management-level roles at companies such as Prologis, CarrAmerica and predecessors to Archstone-Smith, an apartment REIT. Prior thereto, he practiced real estate and transactional law. Mr. Ray received his M.B.A. from the University of Texas at Austin Graduate School of Business, where he was a Longhorn Scholar. He also received a J.D. from the University of Colorado at Boulder School of Law and a B.S. in Business Administration with emphasis in Finance from the University of Denver, where he was a Hornbeck Scholar. In determining Mr. Ray's qualifications to serve on our Board, the Board considered, among other things, Mr. Ray's significant experience with publicly traded REITs and in the acquisition, finance and operation of commercial real estate, as well as over a decade of experience in the data center industry, which provide us with insight into commercial real estate, REIT and data center trends that affect our business.

James A. Attwood, Jr. has served as a director since September 2010. Mr. Attwood is a Managing Director and Head of the Global Telecommunications and Media Group at Carlyle. Prior to joining Carlyle in 2000, Mr. Attwood served as Executive Vice President for Strategy, Development and Planning at Verizon Communications, Inc. ("Verizon"), a telecommunications provider, and GTE Corporation (prior to its merger with Bell Atlantic to form Verizon). Prior to his four years at Verizon

and GTE Corporation, Mr. Attwood served as an investment banker at Goldman, Sachs & Co. for 11 years. Mr. Attwood graduated summa cum laude from Yale University with a B.A. in applied mathematics and an M.A. in statistics. He also received J.D. and M.B.A. degrees from Harvard University. Mr. Attwood currently serves as a member of the boards of directors of Syniverse Holdings, Inc., a provider of business and technology services for the mobile telecommunications industry, Nielsen Holdings N.V., a global information and measurement company, and Getty Images Inc., a global creator and distributor of still imagery, video and multimedia products, which is privately held. Mr. Attwood has gained significant knowledge of the telecommunications industry through his work with Verizon and Carlyle. In determining Mr. Attwood's qualifications to serve on our Board, the Board considered, among other things, Mr. Attwood's private equity experience, together with the experience gained by having served as an officer and on the boards of directors of various telecommunications companies, which provide us with a valuable perspective in monitoring and evaluating our business.

Michael Koehler has served as a director since September 2010. Mr. Koehler currently serves as Senior Vice President, Global Services, of EMC Corporation, a provider of IT consulting services and hardware, a position he has held since August 2011. During 2008 and 2009, Mr. Koehler served as Senior Vice President, Americas Region, of Electronic Data Systems Corporation ("EDS"), a division of the Hewlett-Packard Company ("HP"). EDS, a global provider of information technology and business processing outsourcing services, was acquired by HP in 2008. Prior to HP's acquisition of EDS, Mr. Koehler served as Executive Vice President, Global ITO Services and as Senior Vice President, Infrastructure Technology and Business Process Outsourcing at EDS. During 2007, Mr. Koehler served as Regional Senior Vice President, Europe, Middle East and Africa Operations at EDS, and, from 2006 to 2008, as Enterprise Client Executive, Navy Marine Corps Intranet Account at EDS. From 2004 to 2006, Mr. Koehler served as Chief Operating Officer of The Feld Group, a management information technology consulting firm that was acquired by EDS in 2004. From 1994 to 2001, he held management positions of increasingly greater responsibility at The Feld Group. Mr. Koehler received his B.S. in Industrial Engineering from Texas Tech University. In determining Mr. Koehler's qualifications to serve on our Board, the Board considered, among other things, Mr. Koehler's significant experience in the technology consulting and outsourcing industries and extensive operational and strategic planning experience in complex global companies, which provide us with valuable insight into the technology trends that affect our business.

Paul E. Szurek has served as a director since September 2010. Mr. Szurek has been Chief Financial Officer of Biltmore Farms, LLC, a residential and commercial real estate development and operating company, since 2003. Prior to joining Biltmore Farms, LLC, Mr. Szurek served as Chief Financial Officer of Security Capital Group Incorporated, a publicly-traded real estate investment, development and operating company with exclusive REIT engagement. Mr. Szurek is currently a director of the Charlotte, North Carolina branch of the Federal Reserve Bank of Richmond. He has also previously served as a director to two publicly traded real estate companies, Regency Centers and Security Capital U.S. Realty. Mr. Szurek received a J.D. with honors from Harvard Law School and a B.A. in Government, magna cum laude, from the University of Texas at Austin. In determining Mr. Szurek's qualifications to serve on our Board, the Board considered, among other things, Mr. Szurek's significant experience concerning the acquisition, disposition, financing, operations and market opportunities of private and publicly traded REITs, which provide us with valuable insight into REIT-industry trends that affect our business.

J. David Thompson has served as a director since September 2010. Mr. Thompson has been the Executive Vice President and Chief Information Officer of The Western Union Company, a global payment services company, since April 2012. From 2006 to April 2012, Mr. Thompson was Group President of the Symantec Services Group and Chief Information Officer of Symantec Corporation, a global provider of security, storage, and systems management solutions. From 2004 to 2006,

Mr. Thompson served as Senior Vice President and Chief Information Officer for Oracle Corporation. Mr. Thompson was Senior Vice President and Chief Information Officer at PeopleSoft, Inc. from 1998 to 2005, prior to its acquisition by Oracle Corporation. Mr. Thompson began his career as an officer in the U.S. Air Force as an Intelligence Systems Officer. Mr. Thompson studied computer science at American University. In determining Mr. Thompson's qualifications to serve on our Board, the Board considered, among other things, Mr. Thompson's significant experience in the technology industry and extensive operational experience in information technology systems optimization, which provide us with valuable insights into the information technology trends that affect our business.

David A. Wilson has served as a director since September 2010. Mr. Wilson currently serves as a senior advisor to the Graduate Management Admission Council (the "Council"), where he also served as its President and Chief Executive Officer from 1995 until his retirement in December 2013. The Council is a $100.0 million enterprise that is the owner of the Graduate Management Admission Test, the GMAT. Prior to 1995, he was a Managing Partner and National Director for Professional Development at Ernst & Young LLP, a public accounting firm. From 1968 to 1978, Mr. Wilson held faculty positions at the University of Texas at Austin, where he was awarded tenure, and at Harvard Business School. Mr. Wilson completed his undergraduate studies at Queen's University in Canada, received his M.B.A. at the University of California, Berkeley, and received his doctorate at the University of Illinois. He is a Chartered Accountant in Canada and a Certified Public Accountant in the United States. Mr. Wilson served on the board of directors of Laureate Education, Inc. ("Laureate"), a company which provides access to high-quality, innovative institutions of higher education, from 2002 to 2007, and of Terra Industries, Inc. ("Terra"), a producer and marketer of nitrogen products for the agricultural and industrial markets, from 2009 to 2010. At Laureate, he chaired the Audit Committee and served as a member of the Nominating and Governance Committee and the Conflicts Committee. He served on the Audit Committee of Terra. He has served on the Worldwide Board of Junior Achievement, the Conseil d'Administration de la Confrérie de la Chaîne des Rôtisseurs (Paris) and The Wolf Trap Foundation. He presently serves on the board of directors of Barnes and Noble, Inc., a book retailer and content, commerce and technology company, and as chair of its Audit Committee. In determining Mr. Wilson's qualifications to serve on our Board, the Board considered, among other things, Mr. Wilson's significant industry experience in the areas of accounting policy, internal controls and risk management.

THE BOARD OF DIRECTORS RECOMMENDS A VOTE "FOR" ELECTION OF EACH OF MESSRS. STUCKEY, RAY, ATTWOOD, KOEHLER, SZUREK, THOMPSON AND WILSON.

PROPOSAL TWO: RATIFICATION OF THE APPOINTMENT OF INDEPENDENT
REGISTERED PUBLIC ACCOUNTING FIRM

The Audit Committee of our Board, which is composed entirely of independent directors, has appointed KPMG LLP as our company's independent registered public accounting firm for the fiscal year ending December 31, 2014. Although stockholder approval is not required, we desire to obtain from our stockholders an indication of their approval or disapproval of the Audit Committee's action in appointing KPMG LLP as the independent registered public accounting firm of our company for 2014. If our stockholders do not ratify and approve this appointment, the appointment will be reconsidered by the Audit Committee and our Board.

A representative of KPMG LLP will be present at our Annual Meeting, where the representative will be afforded an opportunity to make a statement and to respond to appropriate questions.

The affirmative vote of a majority of all votes cast on the proposal is necessary to ratify the appointment of KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2014.

The following table summarizes the fees billed by KPMG LLP for professional services rendered to us for fiscal years 2013 and 2012.

Audit Fees. Audit fees consisted of aggregate fees billed for professional services rendered for the audit of our consolidated annual financial statements, review of interim consolidated financial statements, consultations on accounting matters directly related to the audit, or services that are normally provided by the independent registered public accounting firm in connection with statutory and regulatory filings or engagements.

Audit-Related Fees. Audit-related fees consists of aggregate fees billed for accounting consultations and other services that were reasonably related to the performance of audits or reviews of our financial statements and were not reported above under "Audit Fees." The amount for 2012 primarily related to services provided in connection with our 2012 preferred stock offering, and the amount for 2013 related to services provided in connection with registering shares under our equity compensation plan.

The Audit Committee pre-approves all audit and non-audit services provided by our independent registered public accounting firm. Requests to provide services requiring pre-approval by the Audit Committee are submitted to the Audit Committee with a description of the services to be provided and an estimate of the fees to be charged in connection with such services. The Audit Committee pre-approved all services performed by our independent registered accounting firm during fiscal years 2012 and 2013.

THE BOARD OF DIRECTORS RECOMMENDS A VOTE "FOR" THE RATIFICATION OF THE APPOINTMENT OF KPMG LLP AS OUR INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM FOR THE FISCAL YEAR ENDING DECEMBER 31, 2014.

The Audit Committee (the "Audit Committee") of the Board of Directors (the "Board") of CoreSite Realty Corporation (the "Company") assists the Board with its oversight responsibilities regarding the Company's financial reporting process. The Company's management is responsible for the preparation, presentation and integrity of the Company's financial statements and the reporting process, including the Company's accounting policies, internal audit function, internal control over financial reporting and disclosure controls and procedures. KPMG LLP, the Company's independent registered public accounting firm, is responsible for performing an audit of the Company's financial statements.

With regard to the fiscal year ended December 31, 2013, the Audit Committee (i) reviewed and discussed with management our audited consolidated financial statements as of December 31, 2013, and for the year then ended; (ii) discussed with KPMG LLP, the independent auditors, the matters required by PCAOB AU Section 380, Communications with Audit Committees; (iii) received the written disclosures and the letter from KPMG LLP required by applicable requirements of the PCAOB regarding KPMG LLP's communications with the Audit Committee regarding independence; and (iv) discussed with KPMG LLP their independence.

Based on the review and discussions described above, the Audit Committee recommended to our Board that our audited financial statements be included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2013, for filing with the Securities and Exchange Commission.

PROPOSAL THREE: ADVISORY RESOLUTION TO APPROVE THE COMPENSATION OF OUR
NAMED EXECUTIVE OFFICERS

Pursuant to Section 14A of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), our stockholders are entitled to cast an advisory vote at the Annual Meeting to approve the compensation of our named executive officers, as disclosed pursuant to the SEC's compensation disclosure rules, including the "Compensation Discussion and Analysis" section of this proxy statement, or "CD&A," the compensation tables and accompanying narrative disclosures. While this stockholder vote on executive compensation is an advisory vote that is not binding on the company or the Board, we value the opinions of our stockholders and will consider the outcome of the vote when making future compensation decisions. The vote on the advisory resolution to approve the compensation of our named executive officers requires the affirmative vote of a majority of all the votes cast on the proposal.

Our current policy is to provide stockholders with an opportunity to approve the compensation of our named executive officers each year at the annual meeting of stockholders until the next required stockholder vote on the frequency of such votes. We expect that the next such frequency vote will occur at the 2017 annual meeting of stockholders.

As described more fully in the CD&A, our executive compensation program is designed to attract, motivate and retain individuals with the skills required to formulate and drive our strategic direction and achieve annual and long-term performance necessary to create stockholder value. The program also seeks to align executive compensation with stockholder value on an annual and long-term basis through a combination of base pay, annual incentives and long-term incentives. Our practice of placing a significant portion of each executive's compensation at risk demonstrates this pay-for-performance philosophy.

We actively review and assess our executive compensation program in light of the industry in which we operate, the marketplace for executive talent in which we compete, and evolving compensation governance and best practices. We are focused on compensating our executive officers fairly and in a manner that promotes our compensation philosophy and is consistent with our annual and longer-term performance. Specifically, our compensation program for executive officers focuses on the following principal objectives:

Our Board believes that our executive compensation program satisfies these objectives, properly aligns the interests of our executive officers with those of our stockholders, and is worthy of stockholder support. In determining whether to approve this proposal, we believe that stockholders should consider the following:

Accordingly, we ask our stockholders to vote "FOR" the following resolution at the Annual Meeting:

THE BOARD OF DIRECTORS RECOMMENDS A VOTE "FOR" THE ADVISORY RESOLUTION TO
APPROVE THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS.

Our Board currently consists of seven directors. Our charter and bylaws provide that the number of directors constituting our Board may be increased or decreased by a majority vote of our entire Board, provided the number of directors may not be decreased to fewer than one, the minimum number required under the Maryland General Corporate Law ("MGCL") nor, unless our bylaws are amended, more than 15 directors.

Our bylaws require that nominees for director, whether for election by the stockholders or by the Board, shall include such individuals as are entitled to be nominated pursuant to the Operating Partnership Agreement. The Operating Partnership Agreement provides that, for so long as the number of Operating Partnership units and shares of common stock held collectively by the real estate funds affiliated with Carlyle (the "Funds") is equal to or greater than 50% of the total number of shares of outstanding common stock (assuming all Operating Partnership units are exchanged for common stock), certain of the Funds shall have the right to nominate the number of directors that is one less than the lowest whole number that would exceed one-third of the directors, but not less than one director. With the Board having seven members, the Funds presently are entitled to nominate two directors. Such rights to nominate directors are subject to decrease as follows (in each case assuming all Operating Partnership units are exchanged for common stock):

During 2013, the Board held nine meetings. Each member of the Board attended or participated in 75% or more of the aggregate of (i) the total number of meetings of the Board (held during the period for which such person has been a director) and (ii) the total number of meetings held by all committees of the Board on which such person served (during the periods that such person served).

The Board does not have a policy regarding separation of the roles of Chief Executive Officer and Chairman of the Board. The Board believes it is in our best interests to make that determination based on current circumstances. The Board has determined that an independent director serving as Chairman is in our best interests at this time. This structure ensures a greater role of independent directors in the active oversight of our business, including risk management oversight, and in setting agendas and establishing Board priorities and procedures. This structure also allows the Chief Executive Officer to focus to a greater extent on the management of our day-to-day operations. In addition to an independent chairman, our bylaws also require us to have a lead independent director, who may preside over meetings of independent directors in the event of a potential conflict of interest that precludes our chairman from participating. The current lead independent director is Mr. Szurek.

Our non-employee directors met in a special executive session without management at each regularly scheduled Board meeting in 2013, except for a separate meeting of non-employee directors in September 2013 and a meeting in December 2013 in which the non-employee directors met in executive session on the day prior to the Board meeting. Robert G. Stuckey, as Chairman of the Board,

chaired the non-employee director executive sessions held during 2013 and generally chairs any executive sessions held by non-employee directors. The Board expects to continue to conduct an executive session limited to non-employee directors at least annually and our non-employee directors may schedule additional executive sessions in their discretion.

Our Board has a standing Audit Committee, Compensation Committee and Nominating/Corporate Governance Committee. Each of these committees must be composed exclusively of independent directors. The Audit Committee and the Nominating/Corporate Governance Committee must each have at least three directors; the Compensation Committee must have at least two directors. Our Board may from time to time establish other committees to facilitate the management of our company. The Operating Partnership Agreement currently requires that, so long as the Funds collectively own at least 10% of the outstanding common stock (assuming all Operating Partnership units are exchanged for common stock), the Funds shall have the right to have at least one of their nominees on each committee, unless prohibited by law or the rules of the NYSE, other than any committee whose purpose is to evaluate or negotiate any transaction with the Funds. The Funds have exercised this right by requesting that Mr. Stuckey be appointed to the Nominating/Corporate Governance Committee, but have not requested that either of its two nominees be appointed to either the Audit Committee or the Compensation Committee.

The Audit Committee, Compensation Committee and Nominating/Corporate Governance Committee each operate under written charters adopted by the Board. These charters are available on our website at www.coresite.com.

The Audit Committee assists the Board with its oversight responsibilities regarding the integrity of our financial statements, the qualifications and independence of our independent auditor and the performance of our internal audit function and independent auditors. The Audit Committee selects, appoints, assists and meets with the independent auditor, oversees each annual audit and quarterly review, establishes and maintains our internal audit controls and prepares an annual report for inclusion in our annual proxy statement pursuant to federal securities laws. The Audit Committee also works with management regarding risk assessment and risk management, and discusses with management our leverage and any issues that arise with respect to our leverage. Messrs. Wilson, Koehler and Szurek currently serve as members of the Audit Committee, with Mr. Wilson serving as chair. The Board has determined that all three members of the committee are "financially literate" as defined under the NYSE rules, that Mr. Wilson and Mr. Szurek each qualify as an "Audit Committee Financial Expert" as defined under SEC rules, and that all three members of the committee are independent under applicable NYSE and SEC rules for purposes of membership on the Audit Committee. The Audit Committee met seven times in 2013.

The Nominating/Corporate Governance Committee assists the Board in identifying qualified individuals to become directors, makes recommendations to the Board concerning the size, structure and composition of the Board and its committees, monitors the process to assess the Board's effectiveness and is primarily responsible for oversight of corporate governance, including implementing our Corporate Governance Guidelines. In evaluating potential nominees to the Board, the Nominating/Corporate Governance Committee considers, among other things, independence, character, ability to exercise sound judgment, demonstrated leadership, skills, including financial literacy, and experience in the context of the needs of the Board, as well as criteria for Board nominees set forth under "Proposal One: Election of Directors" above. The Nominating/Corporate Governance Committee considers

candidates proposed by stockholders and evaluates them using the same criteria as for other candidates. Messrs. Szurek, Stuckey and Thompson currently serve as members of the Nominating/Corporate Governance Committee, with Mr. Szurek serving as chair. The Board has determined that all three members of the committee are independent under applicable NYSE rules. The Nominating/Corporate Governance Committee met four times in 2013.

At least annually, the Nominating/Corporate Governance Committee evaluates the performance of each current director and considers the results of such evaluation when determining whether to recommend the nomination of such director for an additional term. At an appropriate time prior to each annual meeting at which directors are to be elected or re-elected, the Nominating/Corporate Governance Committee recommends to the Board for nomination by the Board such candidates as the Nominating/Corporate Governance Committee, in the exercise of its judgment, has found to be well qualified and willing and available to serve.

At an appropriate time after a vacancy arises on the Board or a director advises the Board of his or her intention to resign, the Nominating/Corporate Governance Committee will recommend to the Board for election by the Board to fill such vacancy, such prospective member of the Board as the Nominating/Corporate Governance Committee, in the exercise of its judgment, has found to be well qualified and willing and available to serve. In determining whether a prospective member is qualified to serve, the Nominating/Corporate Governance Committee will consider the factors listed above.

The foregoing notwithstanding, if we are legally required by contract or otherwise to permit a third party to designate one or more of the director nominees to be elected (for example, pursuant to rights contained in the Operating Partnership Agreement), then the nomination or election of such directors will be governed by such requirements.

The Compensation Committee reviews and approves the compensation and benefits of our executive officers, administers and makes recommendations to the Board regarding our compensation and stock incentive plans, produces an annual report on executive compensation for inclusion in our annual proxy statement and publishes an annual committee report for our stockholders. Messrs. Koehler, Wilson and Thompson currently serve as members of the Compensation Committee, with Mr. Koehler serving as chair. The Board has determined that all three members of the committee are independent under applicable NYSE and SEC rules for purposes of membership on the Compensation Committee. The Compensation Committee met four times in 2013. For a description of the Compensation Committee's processes and procedures, including the roles of our executive officers and independent compensation consultants in the Compensation Committee's decision-making process, see the section titled "Compensation Discussion and Analysis."

The Board believes that overseeing how the executive team manages the various risks confronting the company is one of its most important areas of oversight. In carrying out this critical responsibility, the Board has designated the Audit Committee with primary responsibility for overseeing enterprise risk management. While the Audit Committee has primary responsibility for overseeing enterprise risk management, each of the other Board committees also considers risk within its area of responsibility. For example, the Nominating/Corporate Governance Committee reviews risks related to legal and regulatory compliance as they relate to corporate governance structure and processes, and the Compensation Committee reviews risks related to compensation matters. The Board is apprised by the committee chairs of significant risks and management's response to those risks via periodic reports. While the Board and its committees oversee risk management strategy, management is responsible for implementing and supervising day-to-day risk management processes and reporting to the Board and its committees on such matters.

With respect to risk related to compensation matters, the Compensation Committee considers, in establishing and reviewing our executive compensation program, whether the program encourages unnecessary or excessive risk taking and has concluded that it does not. Executives' base salaries are fixed in amount and thus do not encourage risk-taking. Bonuses are capped and are tied to overall corporate performance. Any other compensation provided to the executive officers is primarily in the form of long-term equity awards that are important to help further align executives' interests with those of our stockholders. The Compensation Committee believes that these awards do not encourage unnecessary or excessive risk-taking because the ultimate value of the awards is tied to our stock price and because awards are staggered and subject to long-term vesting schedules to help ensure that executives have significant value tied to long-term stock price performance.

The Compensation Committee also has reviewed our compensation programs for employees generally and has concluded that these programs do not create risks that are reasonably likely to have a material adverse effect on the company. The Compensation Committee believes that the design of our annual cash and long-term equity incentives provides an effective and appropriate mix of incentives to help ensure our performance is focused on long-term stockholder value creation and does not encourage the taking of short-term risks at the expense of long-term results. In general, bonus opportunities for our employees are capped, and we have discretion to reduce bonus payments (or pay no bonus) based on individual performance and any other factors we may determine to be appropriate in the circumstances.

The Board has adopted a set of governance guidelines, the CoreSite Realty Corporation Corporate Governance Guidelines, which are designed to promote the continued vitality of the Board and excellence in the execution of its duties. Our Corporate Governance Guidelines establish the practices and procedures of the Board with respect to Board composition and member selection, Board independence, Board meetings and involvement of senior management, management succession planning, Board committees, stock ownership guidelines and the evaluation of senior management and the Board. The Board reviews our Corporate Governance Guidelines at least annually and updates them as necessary to reflect improved corporate governance practices and changes in regulatory requirements. A copy of the Corporate Governance Guidelines is available on our website at www.coresite.com.

Effective January 1, 2014, the Board adopted stock ownership and retention guidelines for all of our executive officers and non-employee directors who are also not employees of Carlyle ("Non-Employee Directors") to further align their interests with our stockholders. Under these guidelines, each of our executive officers is expected to own common stock of the Company with a market value equal to the following amounts for as long as he or she remains an executive officer: Chief Executive Officer—Five times (5.0x) base salary; Other C-Level Executives (CFO, COO, General Counsel)—Three times (3.0x) base salary; and Senior Vice Presidents—One and One-Half times (1.5x) base salary. Non-Employee Directors are expected to own common stock of the Company with a market value equal to five times (5.0x) the value of each Non-Employee Director's annual cash retainer (excluding any annual cash retainer for committee membership or chairmanship). Each executive officer and Non-Employee Director must hold 50% of all net settled shares received from the vesting, delivery or exercise of equity awards from the Company until such executive officer's or Non-Employee Director's stock ownership equals or exceeds the applicable ownership threshold. Executive officers and Non-Employee Directors have until the later to occur of (i) January 1, 2019 or (b) the fifth anniversary of his or her first appointment or election as an executive officer or Non-Employee Director, as applicable, to meet the requirements of these stock ownership guidelines. These stock ownership

guidelines were based on analysis of peer and market practices, as prepared by our independent compensation consultant.

Our Code of Business Conduct and Ethics applies to all of our employees, including our principal executive officer, principal financial officer and principal accounting officer, and the Board. A copy of the Code of Business Conduct and Ethics is available on our website at www.coresite.com. We intend to disclose any changes in or waivers from the Code of Business Conduct and Ethics by posting such information on our website.

The Board determines the form and amount of director compensation after its review of recommendations made by the Compensation Committee. A substantial portion of each director's annual retainer is in the form of equity. During 2013, pursuant to our Non-Employee Director Compensation Policy, and under our 2010 Equity Incentive Award Plan (As Amended and Restated) (the "2010 Plan"), Non-Employee Directors received an annual grant of restricted stock units ("RSUs") having a fair market value as of the date of grant equal to $40,000 and an equal number of tandem dividend equivalents under our 2010 Plan on the date of the annual meeting of stockholders (each, an "Annual RSU Award"). Dividend equivalents give holders the right to receive, upon payment of any ordinary cash dividend paid to holders of our common stock, an equivalent payment in the form of additional RSUs and dividend equivalents. All Annual RSU Awards vest one year from the grant date. Each RSU entitles the director to one share of our common stock payable upon termination of service as a director. In addition, during 2013, each Non-Employee Director was paid an annual cash retainer of $40,000 for services as a director. Directors who are employees of our company or our subsidiaries and those directors nominated by Carlyle do not receive compensation for their services as directors.

During 2013, Non-Employee Directors who served on our Audit, Nominating/Corporate Governance and/or Compensation Committees other than as chair of the committee received an additional annual cash retainer fee of $5,000 for each committee on which they served. Non-Employee Directors who served as the chair of our Audit Committee received an additional annual retainer of $15,000. Non-Employee Directors who served as the chair of one of our other Board committees received an additional annual retainer of $10,000.

The following table presents information regarding the compensation paid during 2013 to Non-Employee Directors who served on the Board during the year. The compensation paid to Mr. Ray is presented below under "Compensation Discussion and Analysis" in the table titled "2013 Summary Compensation Table" and the related explanatory tables. Messrs. Stuckey, Attwood and Ray do not receive any compensation for their services as members of the Board.

In order to bring our non-employee director compensation in line with market compensation, including the non-employee director compensation of our competitors, the Board approved an Amended and Restated Non-Employee Director Compensation Policy (the "Amended Directors Plan") effective January 1, 2014. Under the Amended Directors Plan, Non-Employee Directors will receive an annual grant of RSUs having a fair market value as of the date of grant equal to $75,000 (the "Annual Director RSUs") and an equal number of tandem dividend equivalents as described above under 2013 Director Compensation. The Annual Director RSUs and corresponding dividend equivalents will vest one year from the grant date, subject to such Non-Employee Director's continued service to us as of the vesting date. Each RSU entitles the director to one share of our common stock, and will be payable and settled at the time of vesting, unless a deferral election is made by a Non-Employee Director. Directors who are employees of our company or our subsidiaries and those directors nominated by Carlyle will continue not to receive Annual Director RSUs for their service as directors.

In addition, under the Amended Directors Plan, each Non-Employee Director will receive an annual cash retainer of $75,000 for services as a director. Non-Employee Directors who serve on our Audit, Nominating/Corporate Governance and/or Compensation Committees other than as chair of the committee will receive an additional annual cash retainer fee of $10,000 for each committee on which they serve. Non-Employee Directors who serve as the chair of our Audit Committee or Compensation Committee will receive an additional annual cash retainer of $20,000, and Non-Employee Directors who serve as the chair of the Nominating/Corporate Governance Committee will receive an additional annual cash retainer of $15,000. All annual cash retainers will be paid in quarterly installments subject to such Non-Employee Director's continued service on the Board on each applicable payment date. Directors who are employees of our company or our subsidiaries and those directors nominated by Carlyle will continue not to receive compensation for their service as directors.

These changes to our non-employee director compensation were based on analysis of peer and market practices, as prepared by our independent compensation consultant, and constitute the first changes to our director compensation since our initial public offering in 2010.

Any stockholder or other interested party may contact the Board, including any non-employee director or the non-employee directors as a group, or any individual director or directors, by writing to our Corporate Secretary at 1001 17th Street, Suite 500, Denver, Colorado 80202, with a request to forward the communication to the intended recipient or recipients. In general, any stockholder communication delivered to our Corporate Secretary for forwarding to the Board or specified Board member or members will be forwarded in accordance with the stockholder's instructions. However, our Corporate Secretary reserves the right not to forward to Board members any abusive, threatening or otherwise inappropriate materials. Information regarding the submission of comments or complaints relating to our accounting, internal accounting controls or auditing matters can be found on our website at www.coresite.com.

While we do not have a formal policy requiring our directors to attend stockholder meetings, directors are invited and encouraged to attend all meetings of stockholders. All of our directors attended the 2013 Annual Meeting of Stockholders.

No member of the Compensation Committee is or has ever been an executive officer of the company, and no member of the Compensation Committee had any relationships requiring disclosure by us under the SEC's rules requiring disclosure of certain relationships and related-party transactions. None of our executive officers served on any compensation committee (or its equivalent) of any other entity, the executive officers of which served as a director of the company or a member of our Compensation Committee.

The following table sets forth certain information as of April 9, 2014, regarding our executive officers.

Please see "Proposal One: Election of Directors—Directors" starting on page 5 for information regarding Thomas M. Ray.

Jeffrey S. Finnin has served as our Chief Financial Officer since January 2011. Before joining us in January 2011, Mr. Finnin served as Managing Director and Chief Accounting Officer of Prologis, a publicly held REIT, for over five years. Prior to his tenure at Prologis, Mr. Finnin spent 18 years in public accounting as a partner with KPMG LLP and Arthur Andersen LLP, where he served as the Industry Lead Partner in charge of Real Estate and Financial Services Practices in Denver, Colorado. Mr. Finnin is a Certified Public Accountant and received his B.S. in Business Administration from Colorado State University.

Billie R. Haggard has served as our Senior Vice President, Data Centers since March 2009. In this role, Mr. Haggard is responsible for the design, construction, maintenance, facilities staffing and ultimately uptime, reliability and energy efficiency of our data centers. Mr. Haggard served as our Vice President of Facilities from 2009 to 2010. Prior to joining us in March 2009, Mr. Haggard was the Senior Technical Manager at Switch and Data Facilities Company, Inc. ("Switch and Data"), a provider of network-neutral data centers, where he oversaw all aspects of data center design and management for more than 40 data centers across North America. Prior to joining Switch and Data in 2003, Mr. Haggard held the position of Technical Manager for Lee Technologies, a data center solutions provider, focused upon data center and mission-critical facilities. Mr. Haggard studied Engineering at Louisiana State University and Louisiana Tech University. Additionally, Mr. Haggard held positions of increasing responsibility focused upon nuclear power technology and maintenance during his 14-year career as an officer in the United States Navy. Mr. Haggard was recognized with four Naval Achievement Medals and numerous letters of commendation stemming from his work and teachings concerning highly sensitive, mission-critical facilities.

Derek S. McCandless has served as our Senior Vice President, Legal, General Counsel and Secretary since March 2011. Prior to joining us in March 2011, Mr. McCandless served as Senior Vice President and Assistant General Counsel at Apartment Investment and Management Company, a REIT focused on apartment properties, which he joined in 2003. Prior to his tenure with Apartment Investment and Management Company, Mr. McCandless was in private practice with the law firms of Holme Roberts & Owen LLP (since combined with Bryan Cave LLP) and Cooley LLP. Mr. McCandless received a J.D. from The University of Chicago and a B.S., cum laude, from Brigham Young University.

Robert K. Rockwood has served as our Senior Vice President, General Management since December 2004. Mr. Rockwood has been with us since shortly after the company's founding in 2001. Mr. Rockwood has been involved with many aspects of our data center portfolio development and management and has served as Chief Operating Officer, Chief Investment Officer, SVP of Acquisitions and SVP and General Manager, Eastern Region before assuming his current role. Before joining us in

2001, Mr. Rockwood was Managing Director of the Faris Group, an independent consulting company specializing in increasing the value of data centers and telecom real estate. He was also the director of business development for Broadband Office and the general manager of Transcom, a wholly-owned telecommunications subsidiary of the Columbia Energy Group. Prior to entering the private sector, Mr. Rockwood was a Captain and Commander in the United States Army. Mr. Rockwood received his M.P.A. from the JFK School of Government at Harvard University, his M.S. in construction management from the University of Illinois, and B.S. from the United States Military Academy at West Point.

Steven J. Smith has served as our Senior Vice President, Sales and Sales Enablement since January 2014. Mr. Smith is responsible for overseeing our sales organization, including direct sales, indirect partner channel and sales enablement. Prior to joining us in January 2014, Mr. Smith was a Regional Vice President for SAP AG, a business software company, from March 2008 to January 2013, where he led large enterprise sales across application portfolios, including enterprise resource planning, big data, customer relationship management (CRM), cloud and mobile. From December 2002 to March 2008, he held various roles with Avaya, Inc., a global provider of business communications and collaboration systems, software and services, most recently as Vice President and General Manager of U.S. Channel Sales. Mr. Smith received a B.A. in Marketing and Economics from the University of New Mexico.

Dominic M. Tobin has served as our Senior Vice President, Operations since January 2007. Mr. Tobin is responsible for our company's operations activities, including all Any² Exchange® related initiatives. Mr. Tobin served as our Field Operations Director from 2007 to 2009 and Vice President of Operations from 2009 to 2010. Prior to joining us in January 2007, Mr. Tobin spent 15 combined years at First Level Technology and AT&T, where he held roles of increasing responsibility including Field Operations Director and District Manager. Mr. Tobin obtained his B.S. in Telecommunications Management, magna cum laude, from Golden Gate University. He also received a Network Management Certificate from U.C. Santa Cruz Extension and was a First Class Electronics Technician in the U.S. Coast Guard.

This Compensation Discussion and Analysis is designed to provide our stockholders with a clear understanding of our compensation philosophy and objectives, compensation-setting process, and the 2013 compensation of our named executive officers, or NEOs. For 2013, our NEOs were:

Our compensation program for our NEOs and other executive officers is designed to meet the following primary objectives:

We believe compensation should be structured to ensure that a significant portion of the total compensation opportunity for our named executive officers is directly related to our performance and other factors that directly and indirectly influence stockholder value. For 2013, our fixed compensation versus targeted variable compensation was structured as follows for our CEO and other named executive officers:

We believe our executive compensation should be structured to appropriately balance annual cash compensation with long-term equity-based compensation. For 2013, our target annual cash versus

long-term equity-based compensation was structured as follows for our CEO and other named executive officers:

In addition to the financial highlights above, we achieved the following in 2013:

At our annual meeting of stockholders in May 2013, we held a vote on an advisory resolution to approve the compensation of our named executive officers ("say-on-pay"). The compensation of our named executive officers reported in our 2013 proxy statement was approved by approximately 97% of the votes cast at the 2013 annual meeting. Our Compensation Committee believes this affirms our stockholders' support of our approach to executive compensation, and the Compensation Committee did not materially change its approach in 2013. The Compensation Committee will continue to consider the outcome of our say-on-pay votes when making future compensation decisions for our named executive officers.

Role of the Board of Directors, the Compensation Committee, Management and Consultant

Our Compensation Committee is charged with, among other things, the responsibility of reviewing executive officer compensation policies and practices to ensure adherence to our compensation

philosophy and objectives and that the total compensation paid to our executive officers is consistent with our performance, fair, reasonable and competitive with companies within our industry. The Compensation Committee's primary responsibilities with respect to determining executive compensation are (i) setting performance targets under all annual bonus and long-term and management incentive compensation plans, including our 2010 Plan; (ii) verifying that performance targets used for any performance-based equity compensation plans have been met before payment of any executive bonus or compensation; (iii) approving all amendments to, and terminations of, all compensation plans and any awards under such plans; (iv) granting any awards under any performance-based annual bonus, long-term incentive compensation and equity compensation plans to executive officers; (v) approving which executive officers and other employees receive awards under our equity and incentive compensation plan(s), including the 2010 Plan; and (vi) conducting an annual review of all compensation plans. All plan reviews include reviewing the plan's administrative costs, reviewing current plan features relative to any proposed new features, and assessing the performance of the plan's internal and external administrators if any duties have been delegated.

The Compensation Committee reviews and considers our Chief Executive Officer's recommendations with respect to compensation decisions for our named executive officers other than himself. The Compensation Committee believes it is valuable to consider the recommendations of our Chief Executive Officer with respect to these matters because, given his knowledge of our operations, the data center industry and the day-to-day responsibilities of our executive officers, he is in a unique position to provide the Compensation Committee perspective into the performance of our executive officers in light of our business at a given point in time. The Board and Compensation Committee make all compensation decisions with regard to our Chief Executive Officer.

As part of the 2013 compensation process, the Compensation Committee retained W.T. Haigh & Company, Inc. ("W.T. Haigh") as its independent compensation consultant. W.T. Haigh provides us advisory services only with respect to executive compensation, and works with management only with the approval and under the direction of the Compensation Committee. W.T. Haigh reviewed the compensation components of our 2013 program for our named executive officers and advised the Compensation Committee regarding the components and levels of the executive compensation program, including our incentive and equity-based compensation plans. A representative of W.T. Haigh attended the meetings of the Board and Compensation Committee in February, March and December 2013, and February and March 2014, and continues to make himself available on an ongoing basis to provide guidance to the Compensation Committee on compensation issues as they arise. The Compensation Committee has reviewed its and our company's relationships with W.T. Haigh and has not identified any conflicts of interest.

The Compensation Committee uses peer company data to guide its review of the total compensation of our executive officers and generally reviews the compensation data of our peer companies and industry to understand market competitive compensation. The Compensation Committee focuses on ensuring that the performance-based elements of our executive compensation program are consistent with peer and industry trends. However, the Compensation Committee does not benchmark compensation to a specific percentage of the compensation of peer companies.

In 2013, the Compensation Committee approved a peer group based on analysis and preliminary recommendations by W.T. Haigh. This peer group is comprised of 19 companies in the data center, real estate and general technology industries and the peer group was selected based on a number of criteria, including each company's revenue, market capitalization, number of employees and other key financial metrics. We believe these companies are broadly comparable to us, and appropriately reflect our size, complexity, growth prospects, operations, and labor market for key leadership positions. Our peer group for 2013 was refined versus a broader group of peer companies in 2012 to focus more

exclusively on data center real estate investment trusts and technology companies operating in the colocation, cloud computing and technology services sectors.

The Compensation Committee will review our peer group annually to determine whether changes are necessary to ensure that the peer companies continue to be comparable to us based on changing scope and growth characteristics.

Our compensation program is made up of the following direct compensation elements:

Base Salaries. After the end of 2012, base salaries were reviewed to ensure that they generally were competitive with market levels and generally reflected our level of financial performance during the previous year. No formulaic base salary increases are provided to the NEOs; however, annual merit increases are provided when we determine that such increases are warranted in light of national salary

increase levels, salary levels within our peer companies, individual performance and/or overall company performance.

The base salaries of our named executive officers in 2013, which were effective as of April 1, 2013, were as follows:

Annual Cash Incentive Awards. An important component of our total compensation program is the annual cash incentive based on the achievement of preset, annual company performance objectives and individual executive performance, which is determined in the Compensation Committee's discretion.

In March 2013, the Compensation Committee established the following 2013 target annual incentive amounts for each of our named executive officers under our 2013 annual cash incentive program (the "2013 Bonus Plan"): Mr. Ray—$465,000 (100% of base salary); Mr. Finnin—$219,000 (60% of base salary); Mr. Appleby—$267,750 (75% of base salary); Mr. McCandless—$171,392 (64% of base salary); and Mr. Tobin—$102,500 (50% of base salary). In setting the 2013 target bonus amounts for each of our named executive officers, the Compensation Committee considered the following factors: (i) organizational level and expected impact on our annual operating results; (ii) the scope, level of expertise and experience required for the named executive officer's position; and (iii) competitive levels of target annual incentive opportunity. The 2013 target bonus percentages were unchanged from the target bonus percentages in 2012. Participants under the 2013 Bonus Plan were eligible to receive between 0% and 175% of each participant's respective target bonus.

Actual bonus amounts earned for 2013 were based on the level of company-wide achievement of revenue, earnings before interest, taxes, depreciation and amortization (EBITDA) and funds from operations (FFO) in 2013 versus targets established by the Compensation Committee with management's input at the beginning of the year. The total incentive bonus actually paid to each named executive officer is determined based on the extent to which specified weighted objective company performance goals are achieved, multiplied by a weighting and bonus factor. The bonus

factors for each performance factor used to calculate the total incentive bonuses as approved by the Compensation Committee were as follows:

Results as a Percentage of Target

Revenue	EBITDA	FFO	Multiplier
0% - 89.99%	0% - 87.99%	0% - 84.99%		0	%
90.00% - 90.99%	88.00% - 88.99%	85.00% - 85.99%		25	%
91.00% - 91.99%	89.00% - 89.99%	86.00% - 87.99%		30	%
92.00% - 92.99%	90.00% - 90.99%	88.00% - 88.99%		35	%
93.00% - 93.99%	91.00% - 92.99%	89.00% - 90.99%		40	%
94.00% - 94.99%	93.00% - 93.99%	91.00% - 91.99%		45	%
95.00% - 95.99%	94.00% - 94.99%	92.00% - 93.99%		50	%
96.00% - 96.99%	95.00% - 95.99%	94.00% - 94.99%		60	%
97.00% - 97.99%	96.00% - 97.99%	95.00% - 96.99%		70	%
98.00% - 98.99%	98.00% - 98.99%	97.00% - 97.99%		80	%
99.00% - 99.99%	99.00% - 99.99%	98.00% - 99.99%		90	%
100.00% - 100.99%	100.00% - 100.99%	100.00% - 101.99%		100	%
101.00% - 101.99%	101.00% - 101.99%	102.00% - 102.99%		110	%
102.00% - 102.99%	102.00% - 103.99%	103.00% - 104.99%		120	%
103.00% - 103.99%	104.00% - 104.99%	105.00% - 105.99%		130	%
104.00% - 104.99%	105.00% - 105.99%	106.00% - 107.99%		140	%
105.00% - 105.99%	106.00% - 106.99%	108.00% - 108.99%		150	%
106.00% - 106.99%	107.00% - 108.99%	109.00% - 110.99%		155	%
107.00% - 107.99%	109.00% - 109.99%	111.00% - 111.99%		160	%
108.00% - 108.99%	110.00% - 110.99%	112.00% - 113.99%		165	%
109.00% - 109.99%	111.00% - 111.99%	114.00% - 114.99%		170	%
110.00% or more	112.00% or more	115.00% or more		175	%

The Compensation Committee has the discretion to adjust the actual results based on extraordinary events and/or conditions that either positively or negatively impact our performance. No adjustments were made to the 2013 actual results of the performance factors. In addition, the Compensation Committee may further adjust the bonus payments in its discretion based on each named executive officer's achievement of departmental and individual goals, and overall job performance. The table below sets forth the calculation of the 2013 bonus payouts with respect to the objective company performance goals:

Funds from operations ("FFO") represents net income (computed in accordance with GAAP), excluding gains (or losses) from sales of property and impairment write-downs of depreciable real estate, plus real estate related depreciation and amortization (excluding amortization of deferred financing costs) and after adjustments for unconsolidated partnerships and joint ventures. EBITDA is defined as earnings before interest, taxes, depreciation and amortization ("EBITDA").

In light of our performance in 2013 and the Compensation Committee's discretionary evaluation of each named executive officer's job performance, we paid Messrs. Ray and McCandless approximately

86% of their respective target bonus amounts, Mr. Finnin approximately 99% of his target bonus amount, and Mr. Tobin approximately 104% of his target bonus amount. In connection with his separation from our company in January 2014, Mr. Appleby received a cash bonus of $146,777 (55% of his target bonus amount) under the 2013 Bonus Plan.

Equity Compensation. Generally in the first quarter of each year, the Compensation Committee grants equity-based awards to our named executive officers, other executives and key management personnel in order to align their interests with those of the stockholders and to provide a compensation element intended to retain our named executive officers and other executives over the long term. For 2013, the value of the long-term equity awards granted to each named executive officer was based on the Compensation Committee's assessment of each named executive officer's expected future contributions to our company, ability to impact our long-term results that drive stockholder value, each named executive officer's overall long-term performance and competitive levels of long-term equity compensation for similarly situated executives. Subject to the Board's and the Compensation Committee's discretion, Mr. Appleby's employment agreement provided that his annual equity grant be targeted at three times his base salary.

In February 2013, the Compensation Committee approved equity awards with 60% of the value of the equity award in the form of restricted stock and 40% of the value of the equity award in the form of stock options (using a Black-Scholes valuation to determine the number of stock options). The Compensation Committee believes that the combination of stock options, which only have value if our stock price appreciates, and restricted stock awards, which offer a strong retention incentive and are less dilutive to our current stockholders than stock options, offers an effective equity-based compensation approach for our named executive officers and other executives. The stock options and restricted stock vest in four equal annual installments beginning on the first anniversary of the grant date, subject to continued employment with us.

Changes to 2014 Equity Compensation. In an effort to further our objective to tie executive compensation to the achievement of our corporate strategies and business objectives and to the long-term interests of our stockholders, beginning in 2014, the Compensation Committee awarded a portion of each executive officer's equity compensation in the form of performance-based restricted stock ("PSAs"). The number of PSAs earned is based on our achievement of relative total shareholder return ("TSR") measured versus the MSCI US REIT Index over a three-year performance period, and the number of shares earned under the PSAs may range from 0% to 150%. The PSAs are earned as follows: (i) 20% of the PSAs are earned upon TSR achievement in year one of the performance period, (ii) 20% of the PSAs are earned upon TSR achievement in year two of the performance period, (iii) 20% of the PSAs are earned upon TSR achievement in year three of the performance period, and (iv) 40% of the PSAs are earned upon a cumulative TSR achievement over the three-year performance period. Earned PSAs are released at the end of the three-year performance period provided that the executive officer continues to be employed by us at the end of the performance period. Holders of earned PSAs are also entitled to cash dividends that will be paid at the end of the performance period. This performance share plan is based on analysis of peer and market practices, as prepared by W.T. Haigh, our independent compensation consultant, and is consistent with our performance-based compensation philosophy.

Defined Contribution Plans. We have maintained a Section 401(k) Savings/Retirement Plan (the "401(k) Plan") for eligible employees of our company and any designated affiliate, including our named executive officers. The 401(k) Plan provides our named executive officers and other employees with the opportunity to save for their future retirement by deferring compensation up to IRS imposed limits. We currently make safe harbor contributions to the 401(k) Plan in an amount equal to three percent (3%) of the participant's annual salary and subject to certain other limits. Plan participants vest immediately in the amounts contributed by us. Our employees are eligible to participate in the 401(k) Plan following their first month of full employment, with safe harbor contributions beginning after six months of credited service.

Other Elements of Compensation and Perquisites. In addition to other elements of compensation, as described above, we provide the following benefits to our named executive officers:

We believe that it is important to maintain flexibility to adapt our compensation structure to properly attract, motivate, and retain the top executive talent for which we compete. We may provide compensation components that are different from or in addition to the components described above to our named executive officers, to ensure that we provide a balanced, comprehensive and competitive compensation structure, as deemed appropriate by the Compensation Committee.

ASC Topic 718, Compensation—Stock Compensation (referred to as ASC Topic 718), requires us to recognize an expense for the fair value of equity-based compensation awards. Grants of stock options, restricted stock, restricted stock units and performance units under our equity incentive award plans will be accounted for under ASC Topic 718. Going forward, we expect to consider the accounting implications of significant compensation decisions, especially in connection with decisions that relate to our equity incentive award plans and programs. As accounting standards change, we may revise certain programs to appropriately align accounting expenses of our equity awards with our overall executive compensation philosophy and objectives.

The Compensation Committee (the "Compensation Committee") of the Board of Directors (the "Board") of CoreSite Realty Corporation reviewed and discussed the Compensation Discussion and Analysis included in this proxy statement with management. Based on such review and discussion, the Compensation Committee recommended to the Board that the Compensation Discussion and Analysis be included in this proxy statement for filing with the Securities and Exchange Commission.

The following table sets forth certain information with respect to the compensation paid to our named executive officers during the fiscal years ended December 31, 2013, 2012 and 2011, as applicable. Unless otherwise specified, positions listed below are those currently held by the named executive officers.

Name and Principal Position

Thomas M. Ray	2013	459,327	900,007	600,005	400,000	10,980	2,370,319
President and Chief Executive	2012	443,750	877,506	585,000	638,000	10,064	2,554,320
Officer	2011	425,000	719,998	529,841	689,250	11,058	2,375,147
Jeffrey S. Finnin	2013	362,500	329,994	219,998	216,810	10,980	1,140,282
Chief Financial Officer	2012	353,750	278,404	185,601	293,000	11,911	1,122,666
	2011	329,808	1,089,994	294,301	361,401	8,127	2,083,631
Jarrett Appleby(5)	2013	355,520	600,016	399,996	146,777	7,680	1,509,989
Former Chief Operating Officer	2012	228,846	3,307,098	—	241,000	899	3,777,843
Derek S. McCandless	2013	265,850	288,004	192,002	146,540	10,020	902,416
Senior Vice President, Legal and	2012	257,500	193,191	128,801	265,000	9,939	854,431
General Counsel	2011	201,923	289,994	112,387	237,120	4,698	846,122
Dominic M. Tobin(6)	2013	203,750	150,012	99,999	106,088	8,903	568,752
Senior Vice President, Operations

(1): The amounts included under the "Stock Awards" and "Options Awards" columns reflect the aggregate grant date fair value of the restricted stock awards and option awards to purchase our common stock granted in each respective fiscal year, computed in accordance with FASB ASC Topic 718, excluding the effect of any estimated forfeitures. Assumptions used to calculate these amounts are described in Note 11, "Equity Incentive Plan" to our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2013.
(2): Represents the actual 2013 cash incentive awards earned by each named executive officer under the 2013 Bonus Plan.
(3): Represents company contributions to 401(k) plans, life insurance premiums and parking fees for each named executive officer for 2013.
(4): Previous filings incorrectly reflected cash dividends accrued on unvested restricted stock awards. Because the payment of dividends is factored into the grant date fair value that is reported in the value of the "Stock Awards" in the table above, it is not necessary to include the cash dividends as a component of total compensation. The amounts for 2011 and 2012 under "All Other Compensation" have been amended from previous filings to exclude any accrued dividends on unvested restricted stock awards for each respective named executive officer for each year.
(5): Mr. Appleby was appointed as our Chief Operating Officer effective May 2012, and his employment with us ended effective January 24, 2014.
(6): Mr. Tobin was not a named executive officer of our company in either 2011 or 2012.

The following table presents information regarding plan-based awards granted to our named executive officers for the fiscal year ended December 31, 2013.



				Estimated Future Payouts Under Non-Equity Incentive Plan Awards										Grant Date Fair Value of Stock and Option Awards($)(1)
												Exercise or Base Price of Option Awards($/Sh)
	Award Description
Name	Award Description	Grant Date		Threshold($)		Target($)		Maximum($)
Thomas M. Ray	Annual Cash Incentive				—		465,000		813,750	—	—		—		—
	Restricted Stock		2/28/2013		—		—		—	27,778	—		—		900,007
	Stock Option		2/28/2013		—		—		—	—	60,181		32.40		600,005
Jeffrey S. Finnin	Annual Cash Incentive				—		219,000		383,250	—	—		—		—
	Restricted Stock		2/28/2013		—		—		—	10,185	—		—		329,994
	Stock Option		2/28/2013		—		—		—	—	22,066		32.40		219,998
Jarrett Appleby	Annual Cash Incentive						267,750		468,563	—	—		—		—
	Restricted Stock		2/28/2013		—		—		—	18,519	—		—		600,016
	Stock Option		2/28/2013		—		—		—	—	40,120		32.40		399,996
Derek S. McCandless	Annual Cash Incentive				—		171,392		299,936	—	—		—		—
	Restricted Stock		2/28/2013		—		—		—	8,889	—		—		288,004
	Stock Option		2/28/2013		—		—		—	—	19,258		32.40		192,002
Dominic M. Tobin	Annual Cash Incentive				—		102,500		179,375	—	—		—		—
	Restricted Stock		2/28/2013		—		—		—	4,630	—		—		150,012
	Stock Option		2/28/2013		—		—		—	—	10,030		32.40		99,999

Narrative Disclosure to Summary Compensation Table and Grants of Plan-Based Awards Table

Amounts in the "Non-Equity Incentive Plan Compensation" column of the 2013 Summary Compensation Table represent the actual 2013 cash incentive award earned by each named executive officer under the 2013 Bonus Plan. Amounts in the "Estimated Future Payouts Under Non-Equity Incentive Plan Awards" columns of the 2013 Grants of Plan-Based Awards Table represent the target cash incentive award opportunity for each named executive officer under the 2013 Bonus Plan. See "Annual Cash Incentive Awards" above for a more detailed description of the 2013 Bonus Plan.

Thomas M. Ray—On August 1, 2010, we entered into an employment agreement with Thomas M. Ray, our President and Chief Executive Officer. The agreement has an initial one-year term, subject to automatic annual renewal, unless either party elects to terminate the agreement by providing at least 90 days' notice prior to the applicable anniversary date. The agreement provides for an initial annual base salary of $250,000 and contains other customary employment terms including base salaries, bonuses and other incentive compensation and other benefits. Mr. Ray's employment agreement provides for an initial target annual performance bonus amount of $375,000, subject to adjustment at the discretion of the Board based on achievement of performance goals.

Mr. Ray's employment agreement also provides for, among other things, severance payments and the continuation of certain benefits following certain terminations of employment by us or the termination of employment for "Good Reason" by Mr. Ray. Under these provisions, if Mr. Ray's employment is terminated by us without "Cause," or in connection with our non-renewal of the agreement, or Mr. Ray resigns for Good Reason, Mr. Ray will have the right to receive continued payment of his base salary and the continuation of health benefits at our expense for a period of 18 months following termination. In addition, Mr. Ray would receive a pro-rated lump sum payment upon termination in respect of his performance bonus amount for the year of termination. Mr. Ray also would be entitled to accelerated vesting of any outstanding unvested equity awards that would have vested based on the passage of time had he remained employed for 18 months after termination, and

any of Mr. Ray's stock options would remain exercisable for at least a year following termination. Mr. Ray's employment agreement provides that if he is terminated by us without Cause, or in connection with our non-renewal of the agreement, or he resigns for Good Reason, in each case within 60 days prior to or 12 months following a change in control of our company, then in addition to the payments and benefits described above, he would also receive an additional payment equal to his target performance bonus amount for the year of termination. In addition, the salary continuation amount described above would be paid in a lump sum and Mr. Ray would receive accelerated vesting of all of his outstanding unvested equity awards. In addition, Mr. Ray's employment agreement provides that if his employment is terminated due to his death or disability, he will receive a pro-rated lump sum payment in respect of his target bonus amount for the year of termination and accelerated vesting of any of his outstanding unvested equity awards that would have vested based on the passage of time if he had remained employed with us for 12 months following his termination.

Mr. Ray's employment agreement also contains certain confidentiality covenants prohibiting Mr. Ray from, among other things, disclosing confidential information relating to us. The employment agreement also contains non-competition and non-solicitation restrictions, pursuant to which Mr. Ray will not be permitted to compete with us in certain circumstances for a period of 12 months following his termination of employment for any reason.

Jeffrey S. Finnin—On January 24, 2011, Mr. Finnin became our Chief Financial Officer and he entered into an executive employment agreement with us, with an initial one-year term, subject to automatic annual renewal, unless either party provides 90 days' notice of non-renewal. Mr. Finnin's employment agreement provides for an initial annual base salary of $350,000, an initial target annual performance bonus amount of $210,000 and contains other customary employment terms and benefits.

Mr. Finnin's employment agreement also provides for severance payments and certain benefits following certain terminations of employment. If Mr. Finnin is terminated by us without "Cause," or in connection with our non-renewal of his employment agreement, or if he resigns for "Good Reason," he will have the right to receive continued payment of base salary and health benefits at our expense for 12 months after termination. In addition, Mr. Finnin would receive a pro-rated lump sum payment based on his performance bonus amount for the year of termination and accelerated vesting of his unvested equity awards that would have vested in the 12 months after such termination, and his stock options would remain exercisable for at least one year following termination. If such a termination occurs within 60 days prior to, or 12 months following, a change in control of our company, Mr. Finnin would receive a cash payment equal to 125% of his annual base salary on the termination date (subject to certain conditions), a payment equal to his target performance bonus amount for the year, a pro-rated lump sum payment based on his performance bonus amount for the year of termination, continued payment of health benefits at our expense for 12 months after termination and acceleration of all of outstanding unvested equity awards. In addition, Mr. Finnin's employment agreement provides that if his employment is terminated due to his death or disability, he will receive a pro-rated lump sum payment with respect to his target bonus amount for the year of termination and accelerated vesting of any of his outstanding unvested equity awards that would have vested based on the passage of time if he had remained employed with us for 12 months following his termination. In addition, Mr. Finnin's employment agreement contains confidentiality, non-competition and non-solicitation covenants similar to those described above for Mr. Ray.

Derek S. McCandless—On March 11, 2011, Mr. McCandless became our Senior Vice President, Legal, General Counsel and Secretary, and he entered into an executive employment agreement with us, with an initial one-year term, subject to automatic annual renewal, unless either party provides 90 days' notice of non-renewal. Mr. McCandless's employment agreement provides for an initial annual base salary of $250,000, an initial target annual performance bonus amount of $160,000 and contains other customary employment terms and benefits. Mr. McCandless's employment agreement also includes provisions for severance payments, the continuation of certain benefits, the accelerated vesting

of equity awards and extended stock option exercise periods following certain terminations of employment that are substantially identical to those provided in Mr. Finnin's employment agreement. In addition, Mr. McCandless's employment agreement contains confidentiality, non-competition and non-solicitation covenants similar to those described above for Mr. Ray.

Jarrett Appleby—On May 7, 2012, Mr. Appleby became our Chief Operating Officer, and he entered into an executive employment agreement with us, with an initial one-year term, subject to automatic annual renewal, unless either party provides 90 days' notice of non-renewal. Mr. Appleby's employment agreement provides for an initial annual base salary of $350,000, an initial target annual performance bonus amount of $262,500 and contains other customary employment terms and benefits. Mr. Appleby's employment agreement also includes provisions for severance payments, the continuation of certain benefits, the accelerated vesting of equity awards and extended stock option exercise periods following certain terminations of employment that are substantially identical to those provided in Mr. Finnin's employment agreement. In addition, Mr. Appleby's employment agreement contains confidentiality, non-competition and non-solicitation covenants similar to those described above for Mr. Ray. Mr. Appleby's employment with us ended effective January 24, 2014, and in connection with his separation, Mr. Appleby received the termination benefits as set forth in his employment agreement for a termination without cause, which included (i) continued base salary and health benefits for 12 months, (ii) $146,777 for his cash bonus under the 2013 Bonus Plan, (iii) $10,378 for his pro-rated bonus under our 2014 cash incentive program, (iv) accelerated vesting of unvested stock and options awards that would have vested in the 12 months after his termination, and (v) an extended stock option exercise period. In connection with the receipt of these benefits, Mr. Appleby executed a release in favor of our company and its affiliates, and agreed to confidentiality, non-competition and non-solicitation covenants referred to above.

The following table presents information regarding the outstanding equity awards held by each of our named executive officers at December 31, 2013.

		Option Awards									Stock Awards

Name	Grant Date	Number of Securities Underlying Unexercised Options (#) Exercisable		Number of Securities Underlying Unexercised Options (#) Unexercisable			Option Exercise Price ($)		Option Expiration Date		Number of Shares or Units of Stock That Have Not Vested (#)			Market Value of Shares or Units of Stock That Have Not Vested ($)(1)
Thomas M. Ray	9/22/2010		84,375		28,125	(2)		16.00		9/22/2020		—			—
	9/28/2010		—		—			—		—		7,500	(2)		241,425
	3/11/2011		54,176		54,176	(2)		15.23		3/11/2021		—			—
	3/11/2011		—		—			—		—		23,637	(2)		760,875
	4/5/2012		18,750		56,250	(2)		23.99		4/5/2022		—			—
	4/5/2012		—		—			—		—		27,433	(2)		883,068
	2/28/2013		—		60,181	(2)		32.40		2/28/2023		—			—
	2/28/2013		—		—			—		—		27,778	(2)		894,174
Jeffrey S. Finnin	1/24/2011		17,398		8,697	(3)		14.37		1/24/2021		—			—
	1/24/2011		—		—			—		—		19,717	(3)		634,690
	3/11/2011		18,060		18,057	(2)		15.23		3/11/2021		—			—
	3/11/2011		—		—			—		—		7,878	(2)		253,593
	4/5/2012		5,949		17,846	(2)		23.99		4/5/2022		—			—
	4/5/2012		—		—			—		—		8,703	(2)		280,150
	2/28/2013		—		22,066	(2)		32.40		2/28/2023		—			—
	2/28/2013		—		—			—		—		10,185	(2)		327,855
Jarrett Appleby	5/7/2012		—		—			—		—		87,006	(3)		2,800,723
	2/28/2013		—		40,120	(2)		32.40		2/28/2023		—			—
	2/28/2013		—		—			—		—		18,519	(2)		596,127
Derek S. McCandless	3/11/2011		3,284		1,640	(3)		15.23		3/11/2021		—			—
	3/11/2011		—		—			—		—		3,720	(3)		119,747
	3/11/2011		9,030		9,029	(2)		15.23		3/11/2021		—			—
	3/11/2011		—		—			—		—		3,939	(2)		126,796
	4/5/2012		4,129		12,384	(2)		23.99		4/5/2022		—			—
	4/5/2012		—		—			—		—		6,039	(2)		194,395
	2/28/2013		—		19,258	(2)		32.40		2/28/2023		—			—
	2/28/2013		—		—			—		—		8,889	(2)		286,137
Dominic M. Tobin	9/22/2010		14,064		4,686	(2)		16.00		9/22/2020		—			—
	9/28/2010		—		—			—		—		1,250	(2)		40,238
	3/11/2011		8,128		8,125	(2)		15.23		3/11/2021		—			—
	3/11/2011		—		—			—		—		3,545	(2)		114,114
	4/5/2012		2,744		8,230	(2)		23.99		4/5/2022		—			—
	4/5/2012		—		—			—		—		4,014	(2)		129,211
	2/28/2013		—		10,030	(2)		32.40		2/28/2023		—			—
	2/28/2013		—		—			—		—		4,630	(2)		149,040

The following table presents information regarding the vesting of stock awards for each of our named executive officers during 2013. None of our named executive officers exercised any stock options in 2013.

In September 2010, we adopted the Senior Management Severance and Change in Control Program (the "Severance Plan"), in which members of our senior membership team participate, other than Messrs. Ray, Finnin, Appleby and McCandless. The Severance Plan provides that if a participant is terminated by us at any time without "Cause" or resigns for "Good Reason" (each as defined in the Severance Plan), the participant will be entitled to receive the following severance payments and benefits: (i) continued payment of his or her base salary for a period of time equal to three months, plus one additional month for each year of service with us (subject to a maximum of 12 months); (ii) continued payment of health insurance premiums for a similar period of time; and (iii) accelerated vesting of any unvested equity awards that would have vested solely based on the passage of time had the participant remained employed with us for 12 months following termination. If such a termination occurs within 60 days prior to or nine months following a change in control of our company, participants will receive (i) a lump sum payment on termination of one year of the participant's base salary, (ii) a lump sum payment on termination of the participant's target bonus amount for the year of termination, (iii) an additional lump sum payment amount equal to the participant's pro-rated bonus for the year of termination, (iv) continued payment of health insurance premiums for up to 12 months, subject to certain conditions, and (v) accelerated vesting of all outstanding and unvested equity awards held by the participant. Each of the foregoing benefits is conditioned on the participant executing a release of claims in favor of us following termination. The Severance Plan also contains certain confidentiality, non-solicitation and non-competition covenants. The non-competition and non-solicitation covenants take effect following termination for the period in which the participant would have received severance payments, based on an assumed termination (not in connection with a change in control) of the participant's employment by us without Cause on the date the participant's actual termination of employment occurs, and applies regardless of whether severance payments are actually received under the plan.

Messrs. Ray, Finnin, Appleby and McCandless are entitled to severance payments pursuant to the terms of their employment agreements, as set forth under "Employment Agreements" above. The definitions of "Cause" and "Good Reason" in the Severance Plan, as applicable, are substantially similar to the definitions of those terms in Messrs. Ray's, Finnin's, Appleby's and McCandless's employment agreements, other than changes related to differences in reporting relationships.

The following table sets forth an estimate of the payments to be made to our named executive officers in the event any of the terminations described above or a change in control occurs, assuming that the triggering event took place on December 31, 2013, and based on the closing market price of our common stock on December 31, 2013.



Thomas M. Ray
Salary	—	697,500	697,500
Bonus	465,000	465,000	930,000
Acceleration of Stock and Option Awards	2,208,322	3,719,811	4,614,961
Health Insurance	—	20,424	20,424


Total	2,673,322	4,902,735	6,262,885
Jeffrey S. Finnin
Salary	—	365,000	456,250
Bonus	219,000	219,000	438,000
Acceleration of Stock and Option Awards	1,293,788	1,293,788	2,103,727
Health Insurance	—	13,616	13,616


Total	1,512,788	1,891,404	3,011,593
Jarrett Appleby(1)
Salary	—	357,000	446,250
Bonus	267,750	267,750	535,500
Acceleration of Stock and Option Awards	1,549,401	1,549,401	3,396,850
Health Insurance	—	13,616	13,616


Total	1,817,151	2,187,767	4,392,216
Derek S. McCandless
Salary	—	267,800	334,750
Bonus	171,392	171,392	342,784
Acceleration of Stock and Option Awards	457,724	457,724	1,009,571
Health Insurance	—	5,348	5,348


Total	629,116	902,264	1,692,453
Dominic M. Tobin
Salary	—	119,583	205,000
Bonus	—	—	205,000
Acceleration of Stock and Option Awards	—	344,932	713,754
Health Insurance	—	7,943	13,616


Total	—	472,458	1,137,370

The named executive officers do not participate in any pension plans and received no pension benefits during the year ended December 31, 2013, other than with respect to our defined contribution 401(k) plan.

The named executive officers do not participate in any nonqualified deferred compensation plans and received no nonqualified deferred compensation during the year ended December 31, 2013.

The following table sets forth certain information, as of December 31, 2013, concerning shares of our common stock authorized for issuance under our equity compensation plans, which consists only of our 2010 Equity Incentive Award Plan (As Amended and Restated).

The following table sets forth certain information as of March 31, 2014 with respect to the beneficial ownership of our common stock by (i) each person who beneficially holds more than 5% of the outstanding shares of our common stock based solely on our review of SEC filings; (ii) each director or director nominee; (iii) each named executive officer listed in the table titled "2013 Summary Compensation Table" above; and (iv) all directors and executive officers as a group.

The number of shares beneficially owned by each stockholder is determined under SEC rules and generally includes shares for which the holder has voting or investment power. The information does not necessarily indicate beneficial ownership for any other purpose. The percentage of beneficial ownership shown in the following table is based on 21,629,362 outstanding shares of common stock as of March 31, 2014. For purposes of calculating each person's or group's percentage ownership, shares of common stock issuable pursuant to the terms of stock options, Operating Partnership units or restricted stock units exercisable or vesting within 60 days after March 31, 2014 are included as outstanding and beneficially owned for that person or group, but are not treated as outstanding for the purpose of computing the percentage ownership of any other person or group.

Unless otherwise indicated, the address for all persons named below is c/o CoreSite Realty Corporation, 1001 17th Street, Suite 500, Denver, Colorado 80202.

Name of Beneficial Owner

Beneficial holders of 5% or more of our common stock:
The Carlyle Group L.P.	25,275,390	(1)	53.8	%
FMR LLC	2,986,116	(2)	13.8	%
The Vanguard Group Inc.	2,375,216	(3)	11.0	%
BlackRock, Inc.	1,933,712	(4)	8.9	%
Columbia Wagner Asset Management, LLC	1,754,000	(5)	8.1	%
Named Executive Officers, Directors and Director Nominees:
James A. Attwood, Jr.	—		—
Michael Koehler	17,048	(6)	*
Thomas M. Ray	494,662	(7)	2.3	%
Robert G. Stuckey	—		—
Paul E. Szurek	15,798	(6)	*
J. David Thompson	11,298	(6)	*
David A. Wilson	15,798	(6)	*
Jeffrey S. Finnin	170,642	(8)	*
Dominic M. Tobin	77,173	(9)	*
Derek S. McCandless	94,341	(10)	*
Jarrett Appleby	82,480	(11)	*
All current executive officers and directors as a group (13 persons)	1,084,141	(12)	4.9	%

Carlyle Holdings I GP Inc., Carlyle Holdings I GP Sub L.L.C., Carlyle Holdings I L.P., TC Group, L.L.C., TC Group Sub L.P., Carlyle Realty V GP, L.L.C., Carlyle Realty V, L.P., CoreSite CRP V Holdings, LLC, Carlyle Realty III, GP, L.L.C., Carlyle Realty III, L.P., CoreSite CRP III Holdings, LLC, Carlyle Realty IV GP, L.L.C., Carlyle Realty IV, L.P., CoreSite CRP IV Holdings, LLC, CRP IV AIV GP, L.L.C., CRP IV AIV GP, L.P., CRQP IV AIV, L.P., CRP IV-A AIV, L.P., CoreSite CRP IV Holdings (VCOC II), LLC, CoreSite CRP IV Holdings (VCOC I), LLC, CRP III AIV GP, L.L.C., CRP III AIV GP, L.P., CRQP III AIV, L.P. and CoreSite CRP III Holdings (VCOC), LLC. The address of The Carlyle Group L.P. and each of the other entities listed above is c/o The Carlyle Group, 1001 Pennsylvania Ave NW, Suite 220 South, Washington, DC 20004.

(2): Based solely on a Schedule 13G/A filed with the SEC on February 14, 2014. The address of FMR LLC is 245 Summer Street, Boston, MA 02210.
(3): Based solely on a Schedule 13G/A filed with the SEC on February 12, 2014. The address of The Vanguard Group Inc. is 100 Vanguard Blvd., Malvern, PA 19355. Includes 1,448,006 shares reported as beneficially owned by the Vanguard Specialized Funds—Vanguard REIT Index Fund as set forth on a Schedule 13G/A filed with the SEC on February 4, 2014.
(4): Based solely on a Schedule 13G filed with the SEC on January 28, 2014. The shares are beneficially owned by BlackRock, Inc. and its subsidiaries and affiliates, consisting of BlackRock Advisors, LLC, BlackRock Asset Management Canada Limited, BlackRock Asset Management Ireland Limited, BlackRock Fund Advisors, BlackRock Institutional Trust Company, N.A., BlackRock Investment Management (UK) Ltd, BlackRock Investment Management, LLC and BlackRock Japan Co Ltd. The address of BlackRock, Inc. and each of the other entities listed above is 40 East 52nd Street, New York, NY 10022.
(5): Based solely on a Schedule 13G filed with the SEC on February 6, 2014. Columbia Wagner Asset Management, LLC beneficially owns the shares as investment advisor for Columbia Acorn Fund and various other investment companies and managed accounts. The address of Columbia Wagner Asset Management, LLC and Columbia Acorn Fund is 227 West Monroe Street, Suite 3000, Chicago, IL 60606.
(6): Includes (i) 2,500 shares issuable upon the exercise of options that may be exercised within 60 days of March 31, 2014 and (ii) restricted stock units representing the right to receive 8,298 shares payable upon termination of service as a director.
(7): Includes (i) 218,185 shares issuable upon the exercise of options that may be exercised within 60 days of March 31, 2014, (ii) 2,000 shares held by a family trust of which Mr. Ray is a co-trustee and (iii) 41,601 PSAs that are subject to forfeiture based on the achievement of certain company performance metrics.
(8): Includes 70,601 shares issuable upon the exercise of options that may be exercised within 60 days of March 31, 2014 and 11,346 PSAs that are subject to forfeiture based on the achievement of certain company performance metrics.
(9): Includes (i) 34,253 shares issuable upon the exercise of options that may be exercised within 60 days of March 31, 2014, (ii) 6,591 Operating Partnership units redeemable for cash, or at our discretion, into shares of our common stock on a one-for-one basis and (iii) 5,106 PSAs that are subject to forfeiture based on the achievement of certain company performance metrics. The table above assumes the conversion of all Operating Partnership units into shares of our common stock on a one-for-one basis.

Section 16(a) of the Exchange Act requires our executive officers and directors, and persons who own more than ten percent of a registered class of our equity securities, to file reports of securities ownership and changes in such ownership with the SEC. Executive officers, directors and greater than ten percent stockholders also are required by rules promulgated by the SEC to furnish us with copies of all Section 16(a) forms they file.

Based solely upon a review of Forms 3 and 4 and amendments thereto and written representations furnished to us during the most recent fiscal year, no person who at any time during the fiscal year was a director, officer, or beneficial owner of more than 10% of any class of our equity securities failed to file on a timely basis, as disclosed in the above forms, reports required by Section 16(a) of the Exchange Act during the most recent fiscal year.

Immediately prior to the completion of our initial public offering ("IPO"), we entered into a series of transactions with the Funds to create our current organizational structure (the "Restructuring Transactions"). In connection with this restructuring, all of the property and non-cash assets that were then used in the operation of our company's business were contributed by the Funds to our Operating Partnership. In the Restructuring Transactions, the Funds contributed 100% of their ownership interests in the entities that, directly or indirectly, owned or leased all of the properties that comprised our portfolio and all the other non-cash assets used in our business at that time. The aggregate undepreciated book value plus construction in progress of the contributed properties was $586.2 million as of June 30, 2010. In exchange for this contribution, our Operating Partnership issued to the Funds 34,600,000 Operating Partnership units in the aggregate having a total value of $553.6 million, based upon a price of $16.00 per unit. Of these Operating Partnership units, approximately 19.5%, or $108.1 million in value, 11.4%, or $63.2 million in value, and 15.6%, or $86.2 million in value, respectively, were issued to the Funds contributing One Wilshire Holdings, LLC, 900 N. Alameda Holdings, LLC and 12100 Sunrise Valley Drive Holdings, LLC, each of which now holds Operating Partnership units exchangeable into five percent or more of our common stock. All of the Operating Partnership units held by each of these three entities are beneficially held by DBD Investors V, L.L.C. See "Security Ownership of Certain Beneficial Owners and Management."

In connection with the Restructuring Transactions, we entered into an agreement with certain of the Funds granting them certain rights to receive information about us and to consult with and advise us on significant matters so long as they continue to own any Operating Partnership units or shares of our common stock and the number of Operating Partnership units and shares of common stock held collectively by the Funds is equal to or greater than 5% of the total number of shares of outstanding common stock (assuming all Operating Partnership units are exchanged for common stock). This agreement also provides that for so long as the Funds have the right to nominate directors for election to our Board, such rights will be assigned to two of these Funds. The Funds have agreed to maintain the confidentiality of any material non-public information they receive in connection with the foregoing and the Funds will not receive any compensation or expense reimbursement pursuant to this agreement.

In connection with our IPO, we granted the Funds which received Operating Partnership units in the Restructuring Transactions certain registration rights with respect to any shares of our common stock that may be acquired by them in connection with the exchange of units tendered for redemption. An aggregate of 25,275,390 shares of our common stock issuable upon exchange of units issued in the Restructuring Transactions remain subject to a registration rights agreement. The holders of such units are entitled to require us to seek to register all such shares of common stock underlying the units for public sale, subject to certain exceptions, limitations and conditions precedent. We will bear expenses incident to our registration requirements under the registration rights agreement, except that such expenses shall not include any underwriting fees, discounts or commissions, brokerage or sales commissions, or out-of-pocket expenses of the persons exercising the redemption rights or transfer taxes, if any, relating to the sale of such shares. In 2013, we did not incur any costs in connection with the registration of our common stock under the registration rights agreement.

We have agreed with each of the Funds that have directly or indirectly contributed their interests in properties in our portfolio to our Operating Partnership that if we directly or indirectly sell, convey,

transfer or otherwise dispose of all or any portion of these interests in a taxable transaction, we will make an interest-free loan to the contributors in an amount equal to the contributor's tax liabilities, based on an assumed tax rate. Any such loan would be repayable out of the after-tax proceeds (based on an assumed tax rate) of any distribution from the Operating Partnership to, or any sale of Operating Partnership units (or common stock issued by us in exchange for such units) by, the recipient of such loan, and would be non-recourse to the borrower other than with respect to such proceeds. These tax protection provisions apply for a period expiring on the earlier of (i) September 28, 2017 and (ii) the date on which these contributors (or certain transferees) dispose in certain taxable transactions of 90% of the Operating Partnership units that were issued to them in connection with the contribution of these properties.

On September 19, 2012, we licensed space at our LA1 property (Los Angeles, California) to Syniverse Technologies, LLC, a provider of business and technology services for the mobile telecommunications industry and a company that is wholly owned by an affiliate of Carlyle. The license agreement, which the Board and our management believe was entered into upon market terms, provides for a three-year term with a total contract value of approximately $0.4 million. Total revenue was $0.1 million for the year ended December 31, 2013.

In 2013, we began licensing space at our NY1 property (New York, New York) to Beats Music, LLC, a provider of streaming music services and a company that is an affiliate of Carlyle. The license agreement, which the Board and our management believe was entered into upon market terms, provides for a three-year term with a total contract value of approximately $2.0 million. Total revenue was $0.3 million for the year ended December 31, 2013.

We lease 1,520 net rentable square feet of space at our VA1 property (Reston, Virginia) to affiliates of Carlyle. Total revenue was approximately $0.3 million for the year ended December 31, 2013. The Board and our management believe the lease was entered into upon market terms.

Our Code of Business Conduct and Ethics, which applies to all our directors, officers, employees and agents, includes a process for identifying and resolving potential conflicts of interest, including conflicts arising from transactions with related parties. Specifically, our Code of Business Conduct and Ethics requires that any conflict of interest of our directors, executive officers or other principal officer may only be waived by our Board. All transactions disclosed above were reviewed and approved in accordance with our Code of Business Conduct and Ethics and applicable law.

Any proposal of a stockholder intended to be included in our proxy statement for the 2015 Annual Meeting of Stockholders pursuant to SEC Rule 14a-8, must be received by us no later than December 10, 2014, unless the date of our 2015 Annual Meeting of Stockholders is more than 30 days before or after May 29, 2015, in which case the proposal must be received a reasonable time before we begin to print and mail our proxy materials. All proposals should be directed to our Corporate Secretary, at 1001 17th Street, Suite 500, Denver, Colorado 80202.

A stockholder nomination of a person for election to our Board or a proposal for consideration at our 2015 Annual Meeting of Stockholders not intended to be included in our proxy statement pursuant to SEC Rule 14a-8 must be submitted in accordance with the advance notice procedures and other requirements set forth in Section 11 of Article II of our current bylaws. Pursuant to Section 11 of Article II of our current bylaws, we must receive timely notice of the nomination or other proposal in writing by not later than 5:00 p.m., Eastern Time, on December 10, 2014 nor earlier than November 10, 2014. However, in the event that the 2015 Annual Meeting of Stockholders is advanced or delayed by more than 30 days from the first anniversary of the date of the 2014 Annual Meeting of Stockholders, notice by the stockholder to be timely must be received no earlier than the 150th day prior to the date of the meeting and not later than 5:00 p.m., Eastern Time, on the later of the 120th day prior to the date of the meeting or the 10th day following the date of the first public announcement of the meeting. A copy of our bylaws can be obtained from our Corporate Secretary, who can be reached at 1001 17th Street, Suite 500, Denver, Colorado 80202.

The Nominating/Corporate Governance Committee will consider all recommended director candidates submitted to it in accordance with the established procedures, though it will only recommend to the Board as potential nominees those candidates it believes are most qualified. However, the Nominating/Corporate Governance Committee will not consider any director candidate if the candidate's candidacy or, if elected, Board membership, would violate controlling state or federal law.

Any stockholder, including both stockholders of record and beneficial holders who own their shares through a broker, bank or other nominee, who share an address with another holder of our common stock are only being sent one Notice of Internet Availability of Proxy Materials or set of proxy materials, unless such holders have provided contrary instructions. We will deliver promptly upon written or oral request a separate copy of these materials to any holder at a shared address to which a single copy of the proxy materials were delivered. If you wish to receive a separate copy of these materials in the future or if you are receiving multiple copies and would like to receive a single copy, please contact our Corporate Secretary in writing, at 1001 17th Street, Suite 500, Denver, Colorado 80202, or by telephone at (866) 777-2673.

We do not intend to bring before the Annual Meeting any matters other than the proposals specifically described above, and we know of no matters other than those to come before the Annual Meeting. If any other matters properly come before the Annual Meeting, it is the intention of the persons named in the accompanying proxy to vote such proxy in accordance with the recommendation of the our management on such matters, including any matters dealing with the conduct of the Annual Meeting.

THIS PROXY CARD IS VALID ONLY WHEN SIGNED AND DATED. KEEP THIS PORTION FOR YOUR RECORDS DETACH AND RETURN THIS PORTION ONLY TO VOTE, MARK BLOCKS BELOW IN BLUE OR BLACK INK AS FOLLOWS: Signature (Joint Owners) Signature [PLEASE SIGN WITHIN BOX] Date Date To withhold authority to vote for any individual nominee(s), mark “For All Except” and write the number(s) of the nominee(s) on the line below. 0 0 0 0 0 0 0 0 0 0000209616_1 R1.0.0.51160 For Withhold For All All All Except The Board of Directors recommends you vote FOR the following: 1. Election of Directors Nominees 01 Robert G. Stuckey 02 Thomas M. Ray 03 James A. Attwood, Jr. 04 Michael Koehler 05 Paul E. Szurek 06 J. David Thompson 07 David A. Wilson CORESITE REALTY CORPORATION 1001 17TH STREET, SUITE 500 DENVER, CO 80202 VOTE BY INTERNET - www.proxyvote.com Use the Internet to transmit your voting instructions and for electronic delivery of information up until 11:59 P.M. Eastern Time the day before the cut-off date or meeting date. Have your proxy card in hand when you access the web site and follow the instructions to obtain your records and to create an electronic voting instruction form. ELECTRONIC DELIVERY OF FUTURE PROXY MATERIALS If you would like to reduce the costs incurred by our company in mailing proxy materials, you can consent to receiving all future proxy statements, proxy cards and annual reports electronically via e-mail or the Internet. To sign up for electronic delivery, please follow the instructions above to vote using the Internet and, when prompted, indicate that you agree to receive or access proxy materials electronically in future years. VOTE BY PHONE - 1-800-690-6903 Use any touch-tone telephone to transmit your voting instructions up until 11:59 P.M. Eastern Time the day before the cut-off date or meeting date. Have your proxy card in hand when you call and then follow the instructions. VOTE BY MAIL Mark, sign and date your proxy card and return it in the postage-paid envelope we have provided or return it to Vote Processing, c/o Broadridge, 51 Mercedes Way, Edgewood, NY 11717. The Board of Directors recommends you vote FOR proposals 2 and 3. For Against Abstain 2 Ratification of the appointment of KPMG LLP as independent registered public accounting firm for the fiscal year ending December 31, 2014. 3 The advisory resolution to approve the compensation of our named executive officers. NOTE: Such other business as may properly come before the meeting or any adjournment thereof. Please sign exactly as your name(s) appear(s) hereon. When signing as attorney, executor, administrator, or other fiduciary, please give full title as such. Joint owners should each sign personally. All holders must sign. If a corporation or partnership, please sign in full corporate or partnership name, by authorized officer.

0000209616_2 R1.0.0.51160 Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting: The Form 10-K, Notice & Proxy Statement, Letter to Shareholders is/are available at www.proxyvote.com . CORESITE REALTY CORPORATION Annual Meeting of Stockholders May 29, 2014 3:00 p.m., Pacific Time This proxy is solicited on behalf of the Board of Directors The undersigned stockholder of Coresite Realty Corporation (the "Company") hereby appoints Thomas M. Ray and Derek S. McCandless, and each of them, with power to act without the other and with power of substitution, as proxies and attorneys-in-fact and hereby authorizes them to attend the Annual Meeting of Stockholders of the Company to be held May 29, 2014, or any postponement or adjournment thereof (the "Meeting"), with all powers which the undersigned would possess if present at the Meeting, and to cast on behalf of the undersigned all votes that the undersigned is entitled to cast at the Meeting. The undersigned acknowledges receipt of the Notice of Meeting and accompanying Proxy Statement and revokes any proxy heretofore given with respect to the Meeting. THIS PROXY CARD, WHEN PROPERLY EXECUTED, WILL BE VOTED IN THE MANNER DIRECTED HEREIN BY THE UNDERSIGNED. IF NO DIRECTION IS MADE BUT THE CARD IS SIGNED, THIS PROXY CARD WILL BE VOTED FOR THE ELECTION OF ALL NOMINEES UNDER PROPOSAL 1, FOR PROPOSAL 2, AND FOR PROPOSAL 3. THE VOTES ENTITLED TO BE CAST BY THE UNDERSIGNED WILL BE CAST IN THE DISCRETION OF THE PROXYHOLDER ON ANY OTHER MATTER THAT MAY PROPERLY COME BEFORE THE MEETING. Continued and to be marked, dated and signed on reverse side


Filed by the Registrant ý
Filed by a Party other than the Registrant o
Check the appropriate box:
o		Preliminary Proxy Statement
o		Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))
ý		Definitive Proxy Statement
o		Definitive Additional Materials
o		Soliciting Material under §240.14a-12

	2013		2012

Audit Fees	$	737,000	$	690,000
Audit-Related Fees		5,000		71,750
Tax Fees		—		—
All Other Fees		—		—


Total	$	742,000	$	761,750

Name

Michael Koehler	55,000	40,000	95,000
Paul E. Szurek	55,000	40,000	95,000
J. David Thompson	50,000	40,000	90,000
David A. Wilson	60,000	40,000	100,000

Director

Michael Koehler	2,500	8,211
Paul E. Szurek	2,500	8,211
J. David Thompson	2,500	8,211
David A. Wilson	2,500	8,211


Akamai Technologies, Inc.	Alexandria Real Estate Equities, Inc.	BioMed Realty Trust, Inc.
Cogent Communications Group, Inc.	CyrusOne Inc.	Digital Realty Trust, Inc.
Digital River, Inc.	DuPont Fabros Technology, Inc.	Equinix, Inc.
Internap Network Services Corp.	InterXion Holding N.V.	Limelight Networks, Inc.
Perficient, Inc.	Rackspace Hosting, Inc.	Savvis Inc.*
Silicon Graphics International Corp.	TelecityGroup plc	ValueClick, Inc.
Websense, Inc.


		Sincerely,

		THOMAS M. RAY President, Chief Executive Officer and Director


		BY ORDER OF THE BOARD OF DIRECTORS

		DEREK S. MCCANDLESS Secretary


GENERAL INFORMATION REGARDING SOLICITATION AND VOTING			1
General			1
Purposes of the Annual Meeting			2
Stockholders Entitled to Vote			2
How to Vote			2
Attending and Voting at the Annual Meeting			2
Voting Without Attending the Annual Meeting			3
Quorum			3
Required Vote			4
Board Recommendation			4
Revocation of Proxies			4
Voting Results			4
PROPOSAL ONE: ELECTION OF DIRECTORS			5
Nominees for Election as Directors			6
Directors			6
PROPOSAL TWO: RATIFICATION OF THE APPOINTMENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM			9
Principal Accountant Fees and Services			9
Pre-Approval Policies and Procedures			9
Audit Committee Report			10
PROPOSAL THREE: ADVISORY RESOLUTION TO APPROVE THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS			11
INFORMATION ABOUT OUR BOARD OF DIRECTORS AND ITS COMMITTEES			13
Board Leadership Structure			13
Executive Sessions			13
Committees of the Board of Directors			14
Board Oversight of Risk Management			15
Corporate Governance Guidelines			16
Stock Ownership Guidelines			16
Code of Ethics			17
2013 Director Compensation			17
2014 Director Compensation			18
Communications with the Board			19
Attendance of Directors at 2014 Annual Meeting of Stockholders			19
Compensation Committee Interlocks and Insider Participation			19
EXECUTIVE OFFICERS AND COMPENSATION			20
COMPENSATION DISCUSSION AND ANALYSIS			22
Executive Summary			22
Role of the Board of Directors, the Compensation Committee, Management and Consultant			23
Peer Companies			24
Elements of 2013 Compensation			25
2013 Compensation Decisions			25
Other Compensation Components			29
Accounting Considerations			29
Compensation Committee Report			30
2013 Summary Compensation Table			30
2013 Grants of Plan-Based Awards			31
Narrative Disclosure to Summary Compensation Table and Grants of Plan-Based Awards Table			31
2013 Outstanding Equity Awards at Fiscal Year-End Table			34
2013 Option Exercises and Stock Vested Table			35
Potential Payments upon Termination or Change in Control			35
Pension Benefits			37


Nonqualified Deferred Compensation			37
Equity Compensation Plan Information			37
SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT			38
Section 16(a) Beneficial Ownership Reporting Compliance			40
CERTAIN RELATIONSHIPS AND RELATED PARTY TRANSACTIONS			41
The Restructuring Transactions			41
Registration Rights Agreement			41
Tax Protection Agreement			41
Syniverse Agreement			42
Beats Music Agreement			42
Carlyle Agreement			42
Statement of Policy Regarding Transactions with Related Parties			42
MISCELLANEOUS			43
Stockholder Proposals and Nominations			43
Householding			43
Other Matters			44

Name	Position With the Company		Director Since

Robert G. Stuckey	Director and Chairman of the Board	52	2010
Thomas M. Ray	Director and President and Chief Executive Officer	51	2010
James A. Attwood, Jr.	Director	56	2010
Michael Koehler	Director	47	2010
Paul E. Szurek	Director	53	2010
J. David Thompson	Director	47	2010
David A. Wilson	Director	72	2010

Name	Position With the Company

Thomas M. Ray	President and Chief Executive Officer	51
Jeffrey S. Finnin	Chief Financial Officer	50
Billie R. Haggard	Senior Vice President, Data Centers	48
Derek S. McCandless	Senior Vice President, Legal, General Counsel and Secretary	43
Robert K. Rockwood	Senior Vice President, General Management	53
Steven J. Smith	Senior Vice President, Sales and Sales Enablement	49
Dominic M. Tobin	Senior Vice President, Operations	60

Element	Fixed or Variable	Description

Base Salary	Fixed	To attract and retain executives by offering fixed compensation that is competitive with market opportunities and that recognizes each executive's position, role, responsibility and experience.
Annual Incentive	Variable	To motivate and reward the achievement of our annual performance, including objectives related to revenue, EBITDA and FFO.
Equity Awards	Variable	To align executives' interests with the interests of stockholders through equity-based compensation and promote the long-term retention of our executives and key management personnel.

Performance Factor	2013 Target	2013 Actual					Multiplier

Revenue	$244.3 million	$234.8 million	96.1	%	33.3	%	60%	20.0	%
EBITDA	$100.5 million	$100.5 million	100.0	%	33.3	%	100%	33.3	%
FFO	$83.5 million	$85.3 million	102.1	%	33.3	%	110%	36.7	%


TOTAL								90.0	%

	Stock Awards

Name	Number of Shares Acquired on Vesting (#)			Value Realized on Vesting ($)
Thomas M. Ray		39,008			1,343,026
Jeffrey S. Finnin		32,464			1,024,007
Jarrett Appleby		43,503			1,662,250
Derek S. McCandless		12,204			418,569
Dominic M. Tobin		9,008	(1)		310,646

			Weighted-Average Exercise Price of Outstanding Options, Warrants and Rights (b)

Equity compensation plans approved by stockholders	1,133,915		$	19.89	3,686,242
Equity compensation plans not approved by stockholders	—			—	—
Total equity compensation plans	1,133,915	(1)	$	19.89	3,686,242	(1)